Magne Guttormsen

• Bell, Lauren Tracy; Siem, Sunniva; Larsen, Ann-Cecilie; Bürger, A.; Markova, Maria & Ingeberg, V. W. [Show all 12 contributors for this article] (2026). Extracting the nuclear level density and γ-ray strength function of 90Zr. Physical Review C. ISSN 2469-9985. 114(1). doi: 10.1103/p9y9-xxjf. Full text in Research Archive Show summary

  In this work, we have extracted the nuclear level density (NLD) and 𝛾-ray strength function (𝛾⁢SF) using the Oslo method on particle-𝛾 coincidence data from the 90Zr⁢(𝑝,𝑝′⁢𝛾)90Zr ⁢reaction. We have applied the shape method to the same data set, providing a model-independent 𝛾⁢SF and a cross-check on the slope of the Oslo-method NLD and 𝛾⁢SF. Further, we have combined the 𝛾⁢SF from this work with photonuclear data, thus covering the 2.5<𝐸𝛾<18MeV energy range. We see an increase in strength in the region around 𝐸𝛾≈9MeV, consistent with previous (𝛾,𝛾′) and (𝛾,𝑛) data. On the other hand, surprisingly, we do not observe a strong low-energy increase at low transition energies. The resulting NLD and 𝛾⁢SF were used as inputs to the nuclear reaction code talys to estimate the cross sections and astrophysical reaction rates for the 89Zr(𝑛,𝛾)⁢90Zr 89Y⁡(𝑝,𝛾)90Zr reactions. We find good agreement with available experimental cross sections and JINA calculations for the 89Y⁡(𝑝,𝛾) results, but not for the 89Zr⁢(𝑛,𝛾) reaction rate for stellar temperatures above 0.7 GK. Based on our data, we provide a much more narrow uncertainty band for the 89Zr⁢(𝑛,𝛾) cross section and reaction rate.

• Markova, Maria; Larsen, Ann-Cecilie; Neumann-Cosel, P. von; Litvinova, E.; Goriely, S. & Bell, Lauren Tracy [Show all 17 contributors for this article] (2026). Exploring the statistical properties of the neutron-deficient 109In isotope with the Oslo method. Physical Review C. ISSN 2469-9985. 113(4). doi: 10.1103/qrvh-s12k. Full text in Research Archive Show summary

  The nuclear level density and the 𝛾-ray strength function of the neutron-deficient 109In isotope were extracted for the first time with data from the 106Cd⁢(𝛼,𝑝⁢𝛾)⁢109In reaction using a combination of the Oslo and the shape methods. Both quantities are consistent with those of neighboring Cd and Sn nuclei but show substantial discrepancies with currently available model predictions. In contrast to earlier observations in the neighboring isotopic chains, 109In does not exhibit any significant enhancement of the dipole strength near the neutron separation energy. To interpret this feature, random-phase time-blocking approximation calculations have been performed for 109In and the neighboring 110,112Sn nuclei. The experimental data were also employed to estimate cross sections and rates of the radiative neutron- and proton-capture reactions, 108In⁢(𝑛,𝛾)⁢109In and 108Cd⁢(𝑝,𝛾)⁢109In, respectively, with the reaction code talys. Our (𝑝,𝛾) cross section is in excellent agreement with direct measurements over a wide range of proton energies, while the (𝑛,𝛾) cross section demonstrates notable deviations from predictions in the jina reaclib library. The new results on the statistical properties of 109In provide valuable constraints that may help address the problem of large model uncertainties compromising the accuracy of astrophysical 𝑝-process simulations.

• Pathirana, N. D.; Zegers, R. G. T.; Gao, B.; Spyrou, A.; Larsen, Ann-Cecilie & Berg, H. [Show all 19 contributors for this article] (2026). Extraction of neutron-capture cross sections on 92Zr using the charge-exchange Oslo method. Physical Review C. ISSN 2469-9985. 113(1). doi: 10.1103/qdsh-ygry. Full text in Research Archive Show summary

  The 93 Nb (𝑡, 3 He ) reaction at 115 MeV/nucleon was studied to demonstrate that nuclear level densities and 𝛾-ray strength functions can be extracted from charge-exchange reactions at intermediate energies using the Oslo technique. The matrix of excitation energy in 93 Zr , reconstructed from the (𝑡, 3 He ) reaction, versus the energy of 𝛾 rays emitted by the excited 93 Zr nuclei, was obtained in an experiment with the S800 Spectrograph operated in coincidence with the GRETINA 𝛾-ray detector. The extracted level density and 𝛾-ray strength function obtained by applying the Oslo method to this matrix were used to estimate the 92 Zr ⁢(𝑛,𝛾)⁢ 93 Zr cross section by combining the new results with other experimental data and theoretical calculations for 𝐸⁢1 and 𝑀⁢1 strength functions at higher energies. Good agreement with direct measurements of the 92 Zr ⁢(𝑛,𝛾)⁢ 93 Zr cross section was found. The contribution from the upbend in the extracted 𝛾-ray strength function was important to achieve the consistency, as the neutron-capture cross section without this contribution is significantly below the direct measurements otherwise. Since charge-exchange reactions at intermediate energies have long been used for extracting Gamow-Teller strengths, the successful demonstration of the charge-exchange Oslo method enables experiments in which (𝑛,𝛾) cross sections and Gamow-Teller strengths can be measured simultaneously, which is of benefit for astrophysical studies.

• Wiedeking, Mathis; Goriely, Stephane; Guttormsen, Magne; Herwig, Falk; Larsen, Ann-Cecilie & Liddick, Sean N. [Show all 10 contributors for this article] (2025). Unlocking i-process nucleosynthesis by bridging stellar and nuclear physics. Nature Reviews Physics. 7(12), p. 696–712. doi: 10.1038/s42254-025-00885-7. Full text in Research Archive Show summary

  The origin of chemical elements and their abundances across the cosmos remain one of the central questions in physics. The formation of elements heavier than iron is traditionally attributed to three main mechanisms: the slow and rapid neutron-capture processes (s and r processes) and the p process (mostly driven by photodisintegration reactions). However, certain astronomical observations reveal elemental abundance patterns inconsistent with these processes. These discrepancies prompted the introduction of the intermediate neutron-capture process (i process), which operates at neutron densities between the s and r processes, and which has emerged as a key area of research. Observations of elemental abundances of stars confirm that the i process does indeed take place. Identifying the required astrophysical conditions and contributions of the i process sensitively depend on neutron-capture reaction rates involving unstable atomic nuclei. Important advancements have been achieved through these new astronomical observations and cutting-edge experimental and analytical techniques in nuclear physics, in addition to models of nuclear physics and nucleosynthesis. State-of-the-art facilities and theoretical models are revolutionizing our ability to explore the i process and offer fresh perspectives on the nuclear behaviour under extreme stellar conditions. This Review underscores the synergy between groundbreaking astronomical and nuclear physics research, bridging nuclear physics and observational astrophysics, and advancing our understanding of i-process nucleosynthesis.

• Guttormsen, Magne Sveen (2025). Quasicontinuum M1 γ strength as function of nuclear deformation. European Journal of Physics. ISSN 0143-0807. 61. doi: 10.1140/epja/s10050-025-01642-1. Full text in Research Archive Show summary

  In this investigation, we examine the mean transition probabilities of low-energy γ -rays within the quasicontinuum excitation region. Particular emphasis is placed on the low-energy enhancement (LEE) and scissors mode (SM) structures, which are observed in the γ -ray strength function (γ SF). The stable isotopic chain of neodymium includes nuclei that range from nearly spherical to well-deformed shapes. Consequently, analyzing the LEE and SM structures in relation to deformation may elucidate the characteristics of these phenomena. It has been observed that the integrated measured γ -ray strength of the LEE reaches a maximum of B(M1) ≈ 21μ2 N at a deformation of β2 ≈ 0.16, while the SM attains a maximum of B(M1) ≈ 8μ2 N at β2 ≈ 0.3. Furthermore, the two phenomena display different average γ energies. These experimental findings suggest that the origins of the two structures arise from distinct mechanisms.

• Guttormsen, Magne Sveen (2025). The Oslo Cyclotron Laboratory: The Story of a Successful Small University-Based Laboratory. Nuclear Physics News International. 35(1), p. 4–8. doi: 10.1080/10619127.2025.2454213. Full text in Research Archive
• Spyrou, A.; Mücher, D.; Denissenkov, P.A.; Herwig, F.; Good, E.C. & Balk, G. [Show all 32 contributors for this article] (2024). First Study of the Ba 139 (n,γ) Ba 140 Reaction to Constrain the Conditions for the Astrophysical i Process. Physical Review Letters. ISSN 0031-9007. 132(20). doi: 10.1103/PhysRevLett.132.202701. Full text in Research Archive
• Spyrou, A.; Richman, D.; Couture, A.; Fields, C.E.; Liddick, S.N. & Childers, K. [Show all 26 contributors for this article] (2024). Enhanced production of 60Fe in massive stars. Nature Communications. 15(1). doi: 10.1038/s41467-024-54040-4. Full text in Research Archive Show summary

  Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long-lived radioisotopes, such as 60Fe (iron) and 26Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed 60Fe/26Al ratio by γ-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing 60Fe, and one reaction in particular, the neutron-capture on 59Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of 60Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted 60Fe/26Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models.

• Markova, Maria; Larsen, Ann-Cecilie; Neumann-Cosel, Peter von; Litvinova, E.; Choplin, A. & Goriely, S. [Show all 11 contributors for this article] (2024). Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications. Physical Review C. ISSN 2469-9985. 109(5). doi: 10.1103/PhysRevC.109.054311. Full text in Research Archive Show summary

  The 𝛾-ray strength functions (GSFs) and nuclear level densities (NLDs) below the neutron threshold have been extracted for 111–113,116–122,124 Sn from particle-𝛾 coincidence data with the Oslo method. The evolution of bulk properties of the low-lying electric dipole response has been investigated on the basis of the Oslo GSF data and results of a recent systematic study of electric- and magnetic dipole strengths in even-even Sn isotopes with relativistic Coulomb excitation. The obtained GSFs reveal a resonance-like peak on top of the tail of the isovector giant dipole resonance centered at ≈8 MeV and exhausting ≈2% of the classical Thomas-Reiche-Kuhn (TRK) sum. For mass numbers ≥118 the data suggest also a second peak centered at ≈6.5 MeV. It corresponds to 0.1%–0.5% of the TRK sum rule and shows an approximate linear increase with the mass number. In contrast with predictions of the relativistic quasiparticle random-phase and time-blocking approximation calculations, no monotonic increase in the total low-lying 𝐸⁢1 strength was observed in the experimental data from 111 Sn to 124 Sn, demonstrating rather similar strength distributions in these nuclei. The Oslo GSFs and NLDs were further used as inputs to constrain the cross sections and Maxwellian-averaged cross sections of (𝑛,𝛾) reactions in the Sn isotopic chain using talys. The obtained results agree well with other available experimental data and the recommended values from the JINA REACLIB, BRUSLIB, and KADoNiS libraries. Despite relatively small exhausted fractions of the TRK sum rule, the low-lying electric dipole strength makes a noticeable impact on the radiative neutron-capture cross sections in stable Sn isotopes. Moreover, the experimental Oslo inputs for the 121,123 Sn ⁢(𝑛,𝛾) 122,124 Sn reactions were found to affect the production of Sb in the astrophysical 𝑖 process, providing new constraints on the uncertainties of the resulting chemical abundances from multizone low-metallicity asymptotic giant branch stellar models.

• Lewis, R.; Couture, A.; Liddick, S.N.; Spyrou, A.; Bleuel, D.L. & Campo, Lucia Crespo [Show all 18 contributors for this article] (2023). Statistical (n, γ) cross section model comparison for short-lived nuclei. European Physical Journal A. ISSN 1434-6001. 59(3). doi: 10.1140/epja/s10050-023-00920-0. Full text in Research Archive Show summary

  Neutron-capture cross sections of neutron-rich nuclei are calculated using a Hauser–Feshbach model when direct experimental cross sections cannot be obtained. A number of codes to perform these calculations exist, and each makes different assumptions about the underlying nuclear physics. We investigated the systematic uncertainty associated with the choice of Hauser-Feshbach code used to calculate the neutron-capture cross section of a short-lived nucleus. The neutron-capture cross section for 73Zn(n,y)74Zn was calculated using three Hauser-Feshbach statistical model codes: TALYS, CoH, and EMPIRE. The calculation was first performed without any changes to the default settings in each code. Then an experimentally obtained nuclear level density (NLD) and y-ray strength function (ySF) were included. Finally, the nuclear structure information was made consistent across the codes. The neutron-capture cross sections obtained from the three codes are in good agreement after including the experimentally obtained NLD and ySF, accounting for differences in the underlying nuclear reaction models, and enforcing consistent approximations for unknown nuclear data. It is possible to use consistent inputs and nuclear physics to reduce the differences in the calculated neutron-capture cross section from different Hauser-Feshbach codes. However, ensuring the treatment of the input of experimental data and other nuclear physics are similar across multiple codes requires a careful investigation. For this reason, more complete documentation of the inputs and physics chosen is important.

• Markova, Maria; Larsen, Ann-Cecilie; Tveten, Gry Merete; Neumann-Cosel, Peter von; Eriksen, Tomas Kvalheim & Garrote, Frank Leonel Bello [Show all 16 contributors for this article] (2023). Nuclear level densities and γ -ray strength functions of Sn 111,112,113 isotopes studied with the Oslo method. Physical Review C. ISSN 2469-9985. 108(1). doi: 10.1103/PhysRevC.108.014315. Full text in Research Archive Show summary

  The 111,112,113Sn isotopes have been studied with (p,dγ), (p,p′γ), and (d,pγ) reactions to extract the nuclear level densities (NLDs) and γ-ray strength functions (GSFs) of these nuclei below the neutron separation energy by means of the Oslo method. The experimental NLDs for all three nuclei demonstrate a trend compatible with the constant-temperature model below the neutron separation energy while also being in good agreement with the NLDs of neighboring Sn isotopes, obtained previously with the Oslo-type and neutron evaporation experiments. The extracted microcanonical entropies yield ≈1.5 kB entropy of a valence neutron in both 111Sn and 113Sn. Moreover, the deduced microcanonical temperatures indeed suggest a clear constant-temperature behavior above ≈3 MeV in 111,113Sn and above ≈4.5 MeV in 112Sn. We observe signatures for the first broken neutron pairs between 2 and 4 MeV in all three nuclei. The GSFs obtained with the Oslo method are found to be in good agreement below the neutron threshold with the strengths of 112,114Sn extracted in the (p,p′) Coulomb excitation experiments.

• Larsen, Ann-Cecilie; Tveten, Gry Merete; Renstrøm, Therese; Utsunomiya, H.; Algin, E. & Ari-Izumi, T. [Show all 31 contributors for this article] (2023). New experimental constraint on the W 185 (n,γ) W 186 cross section. Physical Review C. ISSN 2469-9985. 108(2). doi: 10.1103/PhysRevC.108.025804. Full text in Research Archive
• Magagula, S.P.E.; Malatji, Kgashane Leroy; Wiedeking, M.; Pellegri, L; Beckmann, Kristine Sønstevold & Garrote, Frank Leonel Bello [Show all 18 contributors for this article] (2023). Investigating the strength of the scissors mode in 151Sm. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. doi: 10.1088/1742-6596/2586/1/012070. Full text in Research Archive Show summary

  Change in nuclei deformation leads to changes in statistical properties such as the nuclear level density (NLD) and γ-ray strength function (γSF). The NLD and γSF of 151Sm were extracted using the Oslo method. The strength of the scissors resonance (SR) and its centroid energy for 151Sm were found to be 2.13 ± 0.60 µ2N and 2.48 ± 0.25 MeV, respectively. These results were used to place the SR of 151Sm and its magnetic dipole strength B(M1)SR into the context of previously measured Sm isotopes.

• Mücher, D.; Spyrou, A.; Wiedeking, M.; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Zeiser, Fabio Balthasar [Show all 25 contributors for this article] (2023). Extracting model-independent nuclear level densities away from stability. Physical Review C. ISSN 2469-9985. 107(1). doi: 10.1103/PhysRevC.107.L011602. Full text in Research Archive
• Pogliano, Francesco; Garrote, Frank Leonel Bello; Larsen, Ann-Cecilie; Berg, Hannah Christine; Gjestvang, Dorthea & Görgen, Andreas [Show all 19 contributors for this article] (2023). Observation of a candidate for the M1 scissors resonance in odd-odd Ho 166. Physical Review C. ISSN 2469-9985. 107(3). doi: 10.1103/PhysRevC.107.034605. Full text in Research Archive Show summary

  The γ -strength function and the nuclear level density for the odd-odd, rare-earth nucleus 166 Ho have been extracted from 163 Dy(α, pγ ) 166 Ho data using the Oslo method. A structure at ≈3 MeV in the γ -strength function is interpreted as the M1 scissors resonance. By employing three different methods we find that its strength depends rather strongly on the modeling of the E 1 strength, while its centroid does not. The 166 Ho scissors resonance parameters are consistent with previous results on other rare-earth nuclei.

• Pogliano, Francesco; Larsen, Ann-Cecilie; Markova, Maria; Garrote, Frank Leonel Bello; Bjørøen, Marianne Møller & Eriksen, Tomas Kvalheim [Show all 17 contributors for this article] (2022). Indirect measurement of the (n,γ) Sb 127 cross section. Physical Review C. ISSN 2469-9985. 106(1). doi: 10.1103/PhysRevC.106.015804. Full text in Research Archive Show summary

  Nuclei in the 135I region have been identified as being a possible bottleneck for the i process. Here we present an indirect measurement for the Maxwellian-averaged cross section of 126Sb(n,γ). The nuclear level density and the γ-ray strength function of 127Sb have been extracted from 124Sn(α,pγ)127Sb data using the Oslo method. The level density in the low-excitation-energy region agrees well with known discrete levels, and the higher-excitation-energy region follows an exponential curve compatible with the constant-temperature model. The strength function between Eγ≈1.5–8.0 MeV presents several features, such as an upbend and a possibly double-peaked pygmy-like structure. None of the theoretical models included in the nuclear reaction code talys seem to reproduce the experimental data. The Maxwellian-averaged cross section for the 126Sb(n,γ)127Sb reaction has been experimentally constrained by using our level-density and strength-function data as input to talys. We observe a good agreement with the jina reaclib, tendl, and bruslib libraries, while the endf/b-viii.0 library predicts a significantly higher rate than our results.

• Naqvi, F.; Karampagia, S.; Spyrou, A.; Liddick, S.N.; Dombos, A.C. & Bleuel, D.l. [Show all 20 contributors for this article] (2022). Total absorption spectroscopy measurement on neutron-rich 74,75Cu isotopes. Nuclear Physics A. ISSN 0375-9474. A1018(122359). doi: 10.1016/j.nuclphysa.2021.122359. Full text in Research Archive
• Garrote, Frank Leonel Bello; Lopez-Martens, Araceli; Larsen, Ann-Cecilie; Deloncle, I.; Péru, Sophie & Zeiser, Fabio [Show all 39 contributors for this article] (2022). Experimental observation of the M1 scissors mode in ²⁵⁴No. Physics Letters B. ISSN 0370-2693. 834. doi: 10.1016/j.physletb.2022.137479. Full text in Research Archive Show summary

  We present the first experimental evidence of the scissors mode in the superheavy nucleus 254No produced in the 208Pb(48Ca, 2nγ))254No reaction. The spectrum of γrays emitted by the excited 254No nuclei shows an enhanced γ-ray yield for transition energies of ≈2.5MeV. By measuring the linear polarization properties of the emitted γrays, we confirm that the transitions in the enhancement region are predominantly of magnetic-dipole character, characteristic for the scissors mode. To further characterize the enhanced γ-ray yield, simulations of the electromagnetic decay of 254No were performed. The observed enhancement is reproduced by including an M1component in the γstrength function with total strength B(M1↑)=11.8(19)μ2N. This is in good agreement with the integrated M1strength from sum-rule estimates and new calculations within the quasi-particle random-phase approximation presented here. Our results provide a stringent test of phenomenological formulae for the scissors mode currently used in stellar nucleosynthesis calculations. We find that those formulae are not satisfactory, and we recommend using sum-rule estimates assuming a rigid-body moment of inertia instead for describing the scissors mode in superheavy nuclei.

• Guttormsen, Magne Sveen; Ay, Kursad Osman; Ozgur, Mustafa; Algin, Emel; Larsen, Ann-Cecilie & Garrote, Frank Leonel Bello [Show all 26 contributors for this article] (2022). Evolution of the γ -ray strength function in neodymium isotopes. Physical Review C. ISSN 2469-9985. 106(3). doi: 10.1103/PhysRevC.106.034314. Full text in Research Archive Show summary

  The experimental γ-ray strength functions (γSFs) of 142,144–151Nd have been studied for γ-ray energies up to the neutron separation energy using the Oslo method. The results represent a unique set of γSFs for an isotopic chain with increasing nuclear deformation. The data reveal how the low-energy enhancement, the scissors mode, and the pygmy dipole resonance evolve with nuclear deformation and mass number. This indicates that the mechanisms behind the low-energy enhancement and the scissors mode are decoupled from each other.

• Markova, Maria; Larsen, Ann-Cecilie; Neumann-Cosel, Peter von; Bassauer, Sergej; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 23 contributors for this article] (2022). Nuclear level densities and γ -ray strength functions in Sn 120,124 isotopes: Impact of Porter-Thomas fluctuations. Physical Review C. ISSN 2469-9985. 106(3). doi: 10.1103/PhysRevC.106.034322. Full text in Research Archive Show summary

  Nuclear level densities (NLDs) and γ-ray strength functions (GSFs) of 120,124Sn have been extracted with the Oslo method from proton-γ coincidences in the (p,p′γ) reaction. The functional forms of the GSFs and NLDs have been further constrained with the Shape method by studying primary γ-transitions to the ground and first excited states. The NLDs demonstrate good agreement with the NLDs of 116,118,122Sn isotopes measured previously. Moreover, the extracted partial NLD of 1− levels in 124Sn is shown to be in fair agreement with those deduced from spectra of relativistic Coulomb excitation in forward-angle inelastic proton scattering. The experimental NLDs have been applied to estimate the magnitude of the Porter-Thomas (PT) fluctuations. Within the PT fluctuations, we conclude that the GSFs for both isotopes can be considered to be independent of initial and final excitation energies, in accordance with the generalized Brink-Axel hypothesis. Particularly large fluctuations observed in the Shape-method GSFs present a considerable contribution to the uncertainty of the method and may be one of the reasons for deviations from the Oslo-method strength at low γ-ray energies and low values of the NLD (below ≈1×103–2×103MeV−1).

• Persch, C.F.; DeYoung, P.A.; Lyons, S.; Spyrou, Artemis; Liddick, Sean N. & Naqvi, F. [Show all 27 contributors for this article] (2021). Beta-decay feeding intensity distributions of 71,73Ni. Physical Review C. ISSN 2469-9985. C103(055808). doi: 10.1103/PhysRevC.103.055808. Full text in Research Archive Show summary

  This paper presents the β-decay feeding intensity distribution and Gamow-Teller transition strength distribution of 71,73Ni. These quantities were measured using the technique of total absorption spectroscopy at the National Superconducting Cyclotron Laboratory with the Summing NaI(Tl) detector. These measurements provide sensitive constraints to theoretical models used to predict β-decay properties far from stability for astrophysical applications. Specifically, for the astrophysical r process, the majority of the involved nuclei are not accessible by current facilities, and the nuclear input is mainly provided by theory. The present work reports on two neutron-rich nickel isotopes in the region where the weak r process is expected to be relevant in stellar nucleosynthesis. The experimental results are compared to two theoretical models, namely the shell model and the quasiparticle random-phase approximation, to help further refine theoretical calculations and aid in future r-process studies.

• Guttormsen, Magne Sveen; Alhassid, Yoram; Ryssens, Wouter; Ay, K.o.; Ozgur, Mustafa & Algin, Emel [Show all 22 contributors for this article] (2021). Strong enhancement of level densities in the crossover from spherical to deformed neodymium isotopes. Physics Letters B. ISSN 0370-2693. 816. doi: 10.1016/j.physletb.2021.136206. Full text in Research Archive Show summary

  Understanding the evolution of level densities in the crossover from spherical to well-deformed nuclei has been a long-standing problem in nuclear physics. We measure nuclear level densities for a chain of neodymium isotopes 142,144−151Nd which exhibit such a crossover. These results represent the most complete data set of nuclear level densities to date for an isotopic chain between neutron shell-closure and towards mid-shell. We observe a strong increase of the level densities along the chain with an overall increase by a factor of ≈150 at an excitation energy of 6 MeV and saturation around mass 150. Level densities calculated by the shell model Monte Carlo (SMMC) are in excellent agreement with these experimental results. Based on our experimental and theoretical findings, we offer an explanation of the observed mass dependence of the level densities in terms of the intrinsic single-particle level density and the collective enhancement.

• Wiedeking, Mathis; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Zeiser, Fabio; Görgen, Andreas & Liddick, Sean N. [Show all 9 contributors for this article] (2021). Independent normalization for gamma-ray strength functions: The shape method. Physical Review C. ISSN 2469-9985. 104(014311). doi: 10.1103/PhysRevC.104.014311. Full text in Research Archive Show summary

  The shape method, a novel approach to obtain the functional form of the γ-ray strength function (γSF), is introduced. In connection with the Oslo method the slope of the nuclear level density (NLD) and γSF can be obtained simultaneously even in the absence of neutron resonance spacing data. The foundation of the shape method lies in the primary γ-ray transitions which preserve information on the functional form of the γSF. The shape method has been applied to 56Fe, 92Zr, and 164Dy, which are representative cases for the variety of situations encountered in typical NLD and γSF studies. The comparisons of results from the shape method to those from the Oslo method demonstrate that the functional form of the γSF is retained regardless of nuclear structure details or Jπ values of the states fed by the primary transitions.

• Malatji, Kgashane Leroy; Beckmann, Kristine Sønstevold; Wiedeking, Mathis; Siem, Sunniva; Goriely, Stephane & Larsen, Ann-Cecilie [Show all 21 contributors for this article] (2021). Statistical properties of the well deformed 153,155Sm nuclei and the scissors resonance. Physical Review C. ISSN 2469-9985. 103(1). doi: 10.1103/PhysRevC.103.014309. Full text in Research Archive Show summary

  The nuclear level densities (NLDs) and the γ-ray strength functions (γSFs) of 153,155Sm have been extracted from (d,pγ) coincidences using the Oslo method. The experimental NLD of 153Sm is higher than the NLD of 155Sm, in accordance with microscopic calculations. The γSFs of 153,155Sm are in fair agreement with QRPA calculations based on the D1M Gogny interaction. An enhancement is observed in the γSF for both 153,155Sm nuclei around 3 MeV in excitation energy and is attributed to the M1 scissors resonance (SR). Their integrated strengths were found to be in the range 1.3–2.1 and 4.4–6.4 μ2N for 153Sm and 155Sm, respectively. The strength of the SR for 155Sm is comparable to those for deformed even-even Sm isotopes from nuclear resonance fluorescence measurements, while that of 153Sm is lower than expected.

• Görgen, Andreas; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Siem, Sunniva; Adli, Erik & Edin, Nina Frederike J [Show all 14 contributors for this article] (2021). The Oslo Cyclotron Laboratory. The European Physical Journal Plus. 136, p. 1–13. doi: 10.1140/epjp/s13360-021-01150-3. Full text in Research Archive Show summary

  Research at the Oslo Cyclotron Laboratory at the University of Oslo is focused on spectroscopy experiments for nuclear structure and nuclear astrophysics using the Oslo Scintillator Array OSCAR. Light-ion beams from the K=35 cyclotron are furthermore used for studies in radiation biology and medical physics, for research and development related to medical isotope production, and for irradiation of materials and electronics components. Here we present an overview of the laboratory and its research infrastructure, give a brief discussion of the respective research programs and methods, and present recent highlights.

• Zeiser, Fabio; Tveten, Gry Merete; Garrote, Frank Leonel Bello; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Ingeberg, Vetle Wegner [Show all 8 contributors for this article] (2021). The gamma-ray energy response of the Oslo Scintillator Array OSCAR. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 985. doi: 10.1016/j.nima.2020.164678. Full text in Research Archive Show summary

  The new Oslo Scintillator Array (OSCAR) has been commissioned at the Oslo Cyclotron Laboratory (OCL). It consists of 30 large volume (⌀ 3.5 × 8 inches) LaBr3(Ce) detectors that are used for 𝛾-ray spectroscopy. The response functions for incident 𝛾 rays up to 20 MeV are simulated with Geant4. In addition, the resolution, and the total and full-energy peak efficiencies are extracted. The results are in very good agreement with measurements from calibration sources and experimentally obtained mono-energetic in-beam 𝛾-ray spectra.

• Markova, Maria; Neumann-Cosel, Neumann-Cosel von; Larsen, A.C.; Bassauer, S.; Görgen, A. & Guttormsen, Magne Sveen [Show all 25 contributors for this article] (2021). Comprehensive Test of the Brink-Axel Hypothesis in the Energy Region of the Pygmy Dipole Resonance. Physical Review Letters. ISSN 0031-9007. 127(18). doi: 10.1103/PhysRevLett.127.182501. Full text in Research Archive Show summary

  The validity of the Brink-Axel hypothesis, which is especially important for numerous astrophysical calculations, is addressed for 116,120,124Sn below the neutron separation energy by means of three independent experimental methods. The γ-ray strength functions (GSFs) extracted from primary γ-decay spectra following charged-particle reactions with the Oslo method and with the shape method demonstrate excellent agreement with those deduced from forward-angle inelastic proton scattering at relativistic beam energies. In addition, the GSFs are shown to be independent of excitation energies and spins of the initial and final states. The results provide a critical test of the generalized Brink-Axel hypothesis in heavy nuclei, demonstrating its applicability in the energy region of the pygmy dipole resonance.

• Gjestvang, Dorthea; Siem, Sunniva; Zeiser, Fabio; Randrup, Jørgen; Vogt, Ramona & Garrote, Frank Leonel Bello [Show all 20 contributors for this article] (2021). The study of prompt fission γ rays at the Oslo Cyclotron Laboratory. The European Physical Journal Conferences. ISSN 2101-6275. doi: 10.1051/epjconf/202125600005. Full text in Research Archive Show summary

  The study of prompt fission γ rays (PFGs) is crucial for understanding the energy and angular momentum distribution in fission, and over the last decade there has been an revived interest in this aspect of fission. We present the new experimental setup at the Oslo Cyclotron Laboratory for detecting PFGs resulting from charged particle-induced fission. Additionally, PFGs from the reaction 240 Pu(d,pf) were measured in April 2018, and the fission gated proton- γ coincidence spectrum is shown. In order to explore the dependence of the PFG emission on the excitation energy and angular momentum of the compound nucleus, we plan several experiments where charged particle reactions are used to induce fission in various plutonium isotopes. The final results will be compared to predictions made by the Fission Reaction Event Yield Algorithm (FREYA) in an upcoming publication, to benchmark the current modelling of both the PFGs and the fission process.

• Gjestvang, Dorthea; Siem, Sunniva; Zeiser, Fabio; Randrup, Jørgen; Vogt, Ramona & Wilson, Jonathan Nicholas [Show all 19 contributors for this article] (2021). Excitation energy dependence of prompt fission γ-ray emission from 241Pu*. Physical Review C. ISSN 2469-9985. 103(3). doi: 10.1103/PhysRevC.103.034609. Full text in Research Archive Show summary

  Prompt fission γ rays (PFGs) resulting from the 240Pu(d,pf) reaction have been measured as a function of fissioning nucleus excitation energy Ex at the Oslo Cyclotron Laboratory. We study the average total PFG multiplicity per fission, the average total PFG energy released per fission, and the average PFG energy. No significant changes in these characteristics are observed over the range 5.75

• Midtbø, Jørgen E.; Zeiser, Fabio; Lima, Erlend; Larsen, Ann-Cecilie; Tveten, Gry Merete & Guttormsen, Magne Sveen [Show all 9 contributors for this article] (2021). A new software implementation of the Oslo method with rigorous statistical uncertainty propagation. Computer Physics Communications. ISSN 0010-4655. 262. doi: 10.1016/j.cpc.2020.107795. Full text in Research Archive Show summary

  The Oslo method comprises a set of analysis techniques designed to extract nuclear level density and average -decay strength function from a set of excitation-energy tagged -ray spectra. Here we present a new software implementation of the entire Oslo method, called OMpy. We provide a summary of the theoretical basis and derive the essential equations used in the Oslo method. In addition to the functionality of the original analysis code, the new implementation includes novel components such as a rigorous method to propagate uncertainties throughout all steps of the Oslo method using a Monte Carlo approach. The resulting level density and -ray strength function have to be normalized to auxiliary data. The normalization is performed simultaneously for both quantities, thus preserving all correlations. The software is verified by the analysis of a synthetic spectrum and compared to the results of the previous implementation, the oslo-method-software.

• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Spyrou, Artemis & Liddick, Sean N. (2020). Experimentally constrained (n, γ) reaction rates relevant to r- and i-process nucleosynthesis. Acta Physica Polonica B. ISSN 0587-4254. 56(3), p. 667–676. doi: 10.5506/APhysPolB.51.667. Full text in Research Archive Show summary

  The element distribution that we observe in the Universe today tells a fascinating story of nucleosynthesis events that have taken place throughout the 13.7-billion-years-long history starting with the Big Bang. It has been known for a long time that radiative neutron-capture reactions play a major role in synthesizing elements heavier than iron. However, many questions remain when it comes to our understanding of neutron-capture processes in extreme stellar environments. In particular, the intermediate and rapid neutron-capture processes are very challenging to describe, as there exist little or no data on the much-needed neutron-capture rates. In this work, we discuss possibilities to obtain indirect, experimental constrains on these rates by means of the Oslo and the β-Oslo methods.

• Kibédi, T.; Alshahrani, B.; Stuchbery, A.E.; Larsen, Ann-Cecilie; Görgen, Andreas & Siem, Sunniva [Show all 20 contributors for this article] (2020). Radiative Width of the Hoyle State from γ -Ray Spectroscopy. Physical Review Letters. ISSN 0031-9007. 125(18). doi: 10.1103/PhysRevLett.125.182701. Full text in Research Archive Show summary

  The cascading 3.21 and 4.44 MeV electric quadrupole transitions have been observed from the Hoyle state at 7.65 MeV excitation energy in 12C, excited by the 12C(p,p′) reaction at 10.7 MeV proton energy. From the proton-γ−γ triple coincidence data, a value of Γrad/Γ=6.2(6)×10−4 was obtained for the radiative branching ratio. Using our results, together with ΓE0π/Γ from Eriksen et al. [Phys. Rev. C 102, 024320 (2020)] and the currently adopted Γπ(E0) values, the radiative width of the Hoyle state is determined as Γrad=5.1(6)×10−3  eV. This value is about 34% higher than the currently adopted value and will impact models of stellar evolution and nucleosynthesis.

• Sánchez, R. Pérez; Jurado, Beatriz; Meot, V; Roig, O; Dupuis, M & Denis-Petit, D [Show all 21 contributors for this article] (2020). Simultaneous Determination of Neutron-Induced Fission and Radiative Capture Cross Sections from Decay Probabilities Obtained with a Surrogate Reaction. Physical Review Letters. ISSN 0031-9007. 125(12). doi: 10.1103/PhysRevLett.125.122502. Full text in Research Archive
• Scholz, P.; Guttormsen, Magne Sveen; Heim, F.; Larsen, Ann-Cecilie; Mayer, J. & Savran, D. [Show all 12 contributors for this article] (2020). Primary γ-ray intensities and γ-strength functions from discrete two-step γ-ray cascades in radiative proton-capture experiments. Physical Review C. ISSN 2469-9985. doi: 10.1103/PhysRevC.101.045806. Full text in Research Archive Show summary

  Background: Reaction rates of radiative capture reactions can play a crucial role in the nucleosynthesis of heavy nuclei in explosive stellar environments. These reaction rates depend strongly on γ-ray decay widths in the reaction products, which are, for nonresonant capture reactions at high excitation energies, derived from the γ-ray strength function and the nuclear level density. Recently, the ratio method was applied to primary γ rays observed from (d,p) reactions and nuclear resonance fluorescence measurements to extract the dipole strength in atomic nuclei and to test the generalized Brink-Axel hypothesis. Purpose: The purpose of this work is to apply the ratio method to primary γ-ray intensities of the 63,65Cu(p,γ) reactions to extract γ-ray strength information on the nuclei 64,66Zn. The impact of spin distribution, total γ-ray decay widths, level densities, and width fluctuations on the application of the ratio method will be discussed. Additionally, by comparing the relative γ-ray strength at different excitation energies, conclusions on the validity of the generalized Brink-Axel hypothesis can be made. Method: The radiative proton capture reaction measurements have been performed at the HORUS γ-ray spectrometer of the University of Cologne at one excitation energy for each reaction. Primary γ-ray intensities have been determined by normalizing secondary γ-ray transitions in two-step cascades using their absolute branching ratio. The ratio method was applied to the measured primary γ-ray intensities as well as to previous measurements by Erlandsson et al. at different excitation energies. Results: The relative strength function curve for 64Zn from our measurement shows no significant deviation from the previous measurement at a different excitation energy. The same is true for 66Zn where both measurements were at almost the same excitation energy. Absolute γ-strength function values have been obtained by normalizing the relative curves to quasiparticle random phase approximation calculations because of the absence of experimental data in the respective energy region. Conclusion: The generalized Brink-Axel hypothesis, i.e., the independence of the strength function on the excitation energy, seems to hold in the studied energy region and nuclei. The method to obtain primary γ-ray intensities from two-step cascade spectra was shown to be a valuable and sensitive tool although its uncertainties are connected to the knowledge of the low-energy level scheme of the investigated nucleus. The scaling in the ratio method should be taken with care, because the relative strength is not a simple sum of fE1 and fM1 but a somewhat complex linear combination dependent on the excitation energy of the nucleus.

• Ingeberg, Vetle Wegner; Siem, Sunniva; Wiedeking, Mathis; Sieja, Kamila; Bleuel, D.l. & Brits, C.P. [Show all 29 contributors for this article] (2020). First application of the Oslo method in inverse kinematics. European Physical Journal A. ISSN 1434-6001. 56. doi: 10.1140/epja/s10050-020-00070-7. Full text in Research Archive Show summary

  The γ-ray strength function (SF) and nuclear level density (NLD) have been extracted for the first time from inverse kinematic reactions with the Oslo method. This novel technique allows measurements of these properties across a wide range of previously inaccessible nuclei. Proton–γ coincidence events from the d(⁸⁷Kr,p)⁸⁶Kr reaction were measured at iThemba LABS and the γSF and NLD in ⁸⁶Kr was obtained. The low-energy region of the γSF is compared to shell-model calculations, which suggest this region to be dominated by M1 strength. The γSF and NLD are used as input parameters to Hauser–Feshbach calculations to constrain (n,γ) cross sections of nuclei using the TALYS reaction code. These results are compared to ⁸⁶Kr(n,γ) data from direct measurements.

• Kullmann, Ina Kristine Berentsen; Larsen, Ann-Cecilie; Renstrøm, Therese; Beckmann, Kristine Sønstevold; Garrote, Frank Leonel Bello & Campo, Lucia Crespo [Show all 13 contributors for this article] (2019). First experimental constraint on the 191Os(n,γ) reaction rate relevant to s-process nucleosynthesis. Physical Review C. ISSN 2469-9985. 99(6). doi: 10.1103/PhysRevC.99.065806. Full text in Research Archive Show summary

  The nuclear level density and γ -decay strength of 192 Os have been extracted using particle- γ coincidence data from the 192 Os ( α , α ′ γ ) 192 Os reaction by means of the Oslo method. The level density is found to be a rather smooth function of excitation energy, approximately following the constant temperature model. The γ -decay strength is compared to photoneutron cross-section data above the neutron separation energy, and to E 1 and M 1 strengths for nuclei in this mass region derived from primary transitions following neutron capture. Our results are in good agreement with these previous data and draw a consistent picture of the γ -strength function in the range E γ ≈ 1.5 – 6 MeV . Using the measured nuclear level density and γ -decay strength as input to the nuclear-reaction code talys, we provide the first experimentally constrained Maxwellian-averaged cross section (MACS) for the 191 Os ( n , γ ) 192 Os reaction relevant to s -process nucleosynthesis. The systematic uncertainties introduced by the normalization procedure of the level density and γ -strength function were investigated and propagated to the calculated Maxwellian-averaged cross section. The obtained result of the Maxwellian-averaged cross section at k B T = 30 keV , ⟨ σ ⟩ n , γ = 1134 ± 375 mb , is in very good agreement with the theoretical estimate provided by the KADoNiS project, giving experimental support to the adopted KADoNiS value. Good agreement is also found with MACS values obtained from other libraries, such as TENDL-2017, ENDF/B-VII.0, and JEFF.

• Zeiser, Fabio; Tveten, Gry Merete; Potel, Gregory; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Laplace, Thibault A. [Show all 22 contributors for this article] (2019). Restricted spin-range correction in the Oslo method: The example of nuclear level density and γ-ray strength function from 239Pu(d, pγ) 240Pu. Physical Review C. ISSN 2469-9985. 100:024305(2), p. 1–9. doi: 10.1103/PhysRevC.100.024305. Full text in Research Archive
• Lyons, Stephanie; Spyrou, Artemis; Liddick, Sean N.; Naqvi, Farheen; Crider, Benjamin P. & Dombos, Alexander C. [Show all 25 contributors for this article] (2019). 69,71Co β-decay strength distributions from total absorption spectroscopy. Physical Review C. ISSN 2469-9985. 100(2), p. 1–10. doi: 10.1103/PhysRevC.100.025806. Full text in Research Archive Show summary

  Background: The rapid neutron capture process is one of the main nucleosynthesis processes of elements heavier than Fe. Uncertainties in nuclear properties, such as masses, half-lives, and β -delayed neutron probabilities can cause orders of magnitude of variation within astrophysical r-process simulations. Presently, theoretical models are used to make global predictions of various nuclear properties for the thousands of nuclei required for these simulations, and measurements are required to benchmark these models, especially far from stability. Purpose: β -decay strength distributions can be used to not only inform astrophysical r-process simulations, but also to provide a stringent test for theoretical calculations. The aim of this work is to provide accurate strength distributions for 69 , 71 Co β decay. Method: The technique of total absorption spectroscopy was used to measure the β decay of 69 , 71 Co for the first time at the National Superconducting Cyclotron Laboratory. The ions were implanted in a double-sided silicon strip detector at the center of the Summing NaI(Tl) detector and identified using standard particle identification methods. The response of the detection system to the β -decay electron and subsequent γ -ray radiation was fit to the observed experimental data using a χ 2 -minimization technique. Results: β -feeding intensities and Gamow-Teller strength distributions were extracted from the fits of the experimental data. The β -decay intensities show that there is a large percentage of feeding to levels above 2 MeV, which have not been observed in previous studies. The resultant β -feeding intensities and Gamow-Teller strength distributions were compared to shell model and quasiparticle random phase approximation (QRPA) calculations. Conclusions: Comparing experimentally determined β -decay strength distributions provides a test of models, which are commonly used for global β -decay properties for astrophysical calculations. This work highlights the importance of performing detailed comparisons of models to experimental data, particularly far from stability and as close to the r-process path as possible.

• Larsen, Ann-Cecilie; Liddick, Sean N.; Spyrou, Artemis; Guttormsen, Magne Sveen; Garrote, Frank Leonel Bello & Midtbø, Jørgen E. [Show all 7 contributors for this article] (2019). The Beta-Oslo Method: ExperimentallyConstrained (n,γ) Reaction RatesRelevant to ther-Process. In Formicola, Alba; Junker, Matthias; Gialanella, Lucio & Imbriani, Gianluca (Ed.), Nuclei in the Cosmos XV. Springer. ISSN 9783030138752. p. 137–140. doi: 10.1007/978-3-030-13876-9_22. Full text in Research Archive
• Voinov, Alexander; Renstrøm, Therese; Bleuel, D.l.; Grimes, S.M.; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 23 contributors for this article] (2019). Level densities of 74,76Ge from compound nuclear reactions. Physical Review C. ISSN 2469-9985. 99(5). doi: 10.1103/PhysRevC.99.054609. Full text in Research Archive Show summary

  The level densities of 74 , 76 Ge nuclei are studied with 68 , 70 Zn ( 7 Li , Xp ) reactions. Proton evaporation spectra are measured at backward angles in a wide energy region, from about 2 to 25 MeV. The analysis of spectra allows for the testing of level density models used in modern reaction codes for practical cross-section calculations. Our results show that at excitation energies above the discrete level region, all level density models tested in this work overestimate the level densities that are needed to reproduce proton spectra from these reactions. The Gilbert and Cameron model, which includes the constant-temperature energy dependence of the level density, shows the best agreement with experiment, however, its parameters need to be adjusted to reflect the observed reduction of the level density at higher excitation energies.

• Brits, C.P.; Malatji, Kgashane L.; Wiedeking, M.; Kheswa, BV; Goriely, S. & Garrote, Frank Leonel Bello [Show all 27 contributors for this article] (2019). Nuclear level densities and γ-ray strength functions of 180,181,182Ta. Physical Review C. ISSN 2469-9985. 99(5). doi: 10.1103/PhysRevC.99.054330. Full text in Research Archive Show summary

  Particle- γ coincidence experiments were performed at the Oslo Cyclotron Laboratory with the 181 Ta ( d , X ) and 181 Ta ( 3 He , X ) reactions to measure the nuclear level densities (NLDs) and γ -ray strength functions ( γ SFs ) of 180 , 181 , 182 Ta using the Oslo method. The back-shifted Fermi-gas, constant temperature plus Fermi gas, and Hartree-Fock-Bogoliubov plus combinatorial models were used for the absolute normalizations of the experimental NLDs at the neutron separation energies. The NLDs and γ SFs are used to calculate the corresponding 181 Ta ( n , γ ) cross sections and these are compared to results from other techniques. The energy region of the scissors resonance strength is investigated and from the data and comparison to prior work it is concluded that the scissors strength splits into two distinct parts. This splitting may allow for the determination of triaxiality and a γ deformation of 14 . 9 ∘ ± 1 . 8 ∘ was determined for 181 Ta .

• Larsen, Ann-Cecilie; Spyrou, Artemis; Liddick, Sean N. & Guttormsen, Magne Sveen (2019). Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis. Progress in Particle and Nuclear Physics. ISSN 0146-6410. 107, p. 69–108. doi: 10.1016/j.ppnp.2019.04.002. Full text in Research Archive Show summary

  The rapid-neutron capture process (r process) is identified as the producer of about 50% of elements heavier than iron. This process requires an astrophysical environment with an extremely high neutron flux over a short amount of time (∼ seconds), creating very neutron-rich nuclei that are subsequently transformed to stable nuclei via β − decay. In 2017, one site for the r process was confirmed: the advanced LIGO and advanced Virgo detectors observed two neutron stars merging, and immediate follow-up measurements of the electromagnetic transients demonstrated an ”afterglow” over a broad range of frequencies fully consistent with the expected signal of an r process taking place. Although neutronstar mergers are now known to be r-process element factories, contributions from other sites are still possible, and a comprehensive understanding and description of the r process is still lacking. One key ingredient to large-scale r-process reaction networks is radiative neutron-capture (n, γ) rates, for which there exist virtually no data for extremely neutronrich nuclei involved in the r process. Due to the current status of nuclear-reaction theory and our poor understanding of basic nuclear properties such as level densities and average γ-decay strengths, theoretically estimated (n, γ) rates may vary by orders of magnitude and represent a major source of uncertainty in any nuclear-reaction network calculation of rprocess abundances. In this review, we discuss new approaches to provide information on neutron-capture cross sections and reaction rates relevant to the r process. In particular, we focus on indirect, experimental techniques to measure radiative neutron-capture rates. While direct measurements are not available at present, but could possibly be realized in the future, the indirect approaches present a first step towards constraining neutron-capture rates of importance to the r process.

• Naqvi, F.; Simon, Anna; Guttormsen, Magne Sveen; Schwengner, R; Frauendorf, S & Reingold, C. S. [Show all 11 contributors for this article] (2019). Nuclear level densities and γ-ray strength functions in samarium isotopes. Physical Review C. ISSN 2469-9985. 99(5). doi: 10.1103/PhysRevC.99.054331. Full text in Research Archive Show summary

  The γ -strength functions and level densities in the quasicontinuum of 147 , 149 Sm isotopes have been extracted from particle- γ coincidences using the Oslo method. The nuclei of interest were populated via (p,d) reactions on pure 148 , 150 Sm targets and the reaction products were recorded by the Hyperion array. An upbend in the low-energy region of the γ SF has been observed. The systematic analysis of the γ SF for a range of Sm isotopes highlights the interplay between scissors mode and the upbend. Shell-model calculations show reasonable agreement with the experimental γ SFs and confirm the correspondence between the upbend and scissors mode.

• Liddick, Sean N.; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Spyrou, Artemis; Crider, Benjamin P. & Naqvi, Farheen [Show all 30 contributors for this article] (2019). Benchmarking the extraction of statistical neutron capture cross sections on short-lived nuclei for applications using the β-Oslo method. Physical Review C. ISSN 2469-9985. 100:024624(2), p. 1–12. doi: 10.1103/PhysRevC.100.024624. Full text in Research Archive Show summary

  Numerous scientific fields including astrophysics, nuclear power, and nuclear forensics require a knowledge of basic nuclear properties for large numbers of short-lived, radioactive isotopes far removed from stable nuclei. Neutron-capture cross sections are one such piece of nuclear data where direct measurements are not possible and theoretical predictions can vary by orders of magnitude. A recently developed indirect technique for inferring neutron capture rates, the β -Oslo method, has been introduced but not compared against a known, directly measured neutron capture cross section. To provide this benchmark, two indirect methods based on β decay and charged-particle reactions were used to extract the nuclear level density and γ -ray strength function of 51 Ti . The nuclear level density and γ -ray strength function from the two data sets were found to be equivalent and were used to extract the neutron capture cross section of 50 Ti which agrees with previous direct measurements at high neutron energies. The results demonstrate the validity of the β -Oslo method for extracting neutron capture cross sections of short-lived nuclei and provide a sufficiently small uncertainty to be used in various applications.

• Guttormsen, Magne Sveen; Goriely, Stephane; Larsen, Ann-Cecilie; Görgen, Andreas; Hagen, Trine Wiborg & Renstrøm, Therese [Show all 13 contributors for this article] (2019). Indirect(n,γ)91,92Zr Cross SectionMeasurements for the s-Process. In Formicola, Alba; Junker, Matthias; Gialanella, Lucio & Imbriani, Gianluca (Ed.), Nuclei in the Cosmos XV. Springer. ISSN 9783030138752. p. 359–362. doi: 10.1007/978-3-030-13876-9_65. Full text in Research Archive
• Wrzosek-Lipska, K.; Rezynkina, K.; Bree, N.; Zielińska, M.; Gaffney, L.P. & Petts, A. [Show all 70 contributors for this article] (2019). Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes: Coulomb excitation of ¹⁸²Hg, ¹⁸⁴Hg, ¹⁸⁶Hg and ¹⁸⁸Hg. European Physical Journal A. ISSN 1434-6001. 55(8), p. 1–23. doi: 10.1140/epja/i2019-12815-2. Full text in Research Archive
• Malatji, Kgashane Leroy; Wiedeking, Mathis; Goriely, Stephane; Brits, Christiaan Petrus; Kheswa, Bonginkosi Vincent & Garrote, Frank Leonel Bello [Show all 22 contributors for this article] (2019). Re-estimation of 180Ta nucleosynthesis in light of newly constrained reaction rates. Physics Letters B. ISSN 0370-2693. 791, p. 403–408. doi: 10.1016/j.physletb.2019.03.013. Full text in Research Archive
• Lewis, Rebecca; Liddick, Sean N.; Larsen, Ann-Cecilie; Spyrou, Artemis; Bleuel, Darren L. & Couture, Aaron J. [Show all 17 contributors for this article] (2019). Experimental constraints on the 73Zn(n,γ)74Zn reaction rate. Physical Review C. ISSN 2469-9985. 99(3). doi: 10.1103/PhysRevC.99.034601. Full text in Research Archive Show summary

  Background: The recent observation of a neutron-star merger finally confirmed one astrophysical location of the rapid neutron-capture process (r-process). Evidence of the production of A < 140 nuclei was seen, but there is still little detailed information about how those lighter elements are produced in such an environment. Many of the questions surrounding the A ≈ 80 nuclei are likely to be answered only when the nuclear physics involved in the production of r-process nuclei is well understood. Neutron-capture reactions are an important component of the r-process, and neutron-capture cross sections of r-process nuclei, which are very neutron rich, have large uncertainties. Purpose: Indirectly determine the neutron-capture cross section and reaction rate of 73Zn(n, γ ) 74Zn. Methods: The nuclear level density (NLD) and γ -ray strength function (γ SF) of 74Zn were determined following a total absorption spectroscopy (TAS) experiment focused on the β decay of 74Cu into 74Zn performed at the National Superconducting Cyclotron Laboratory. The NLD and γ SF were used as inputs in a Hauser-Feshbach statistical model to calculate the neutron-capture cross section and reaction rate. Results: The NLD and γ SF of 74Zn were experimentally constrained for the first time using β-delayed γ rays measured with TAS and the β-Oslo method. The NLD and γ SF were then used to constrain the neutron-capture cross section and reaction rate for the 73Zn(n, γ ) 74Zn reaction. Conclusions: The uncertainty in the neutron-capture cross section and reaction rate of 73Zn(n, γ ) 74Zn calculated in TALYS was reduced to under a factor of 2 from a factor of 5 in the cross section and a factor of 11 in the reaction rate using the experimentally obtained NLD and γ SF.

• Utsunomiya, Hiroaki; Renstrøm, Therese; Tveten, Gry Merete; Goriely, Stéphane; Katayama, Seitaro & Ari-Izumi, Takashi [Show all 22 contributors for this article] (2018). Photoneutron cross sections for Ni isotopes: Toward understanding (n, γ ) cross sections relevant to weak s-process nucleosynthesis. Physical Review C. ISSN 2469-9985. 98(5), p. 1–9. doi: 10.1103/PhysRevC.98.054619. Full text in Research Archive Show summary

  Photoneutron cross sections were measured for 58Ni, 60Ni, 61Ni, and 64Ni at energies between the one-neutron and two-neutron thresholds using quasimonochromatic γ -ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. These photoneutron data are used to extract the γ -ray strength function above the neutron threshold, complementing the information obtained by the Oslo method below the threshold. We discuss radiative neutron-capture cross sections and the Maxwellian-averaged cross sections for Ni isotopes including 63Ni, a branching point nucleus along the weak s-process path. The cross sections are calculated with the experimentally constrained γ-ray strength functions from the Hartree-Fock-Bogolyubov plus quasiparticle–random-phase approximation based on the Gogny D1M interaction for both E1 and M1 components and supplemented with the M1 upbend.

• Jones, M.D.; Macchiavelli, Augusto Oswaldo; Wiedeking, Mathis; Bernstein, Lee A.; Crawford, Heather L. & Campbell, C.M. [Show all 30 contributors for this article] (2018). Examination of the Low-Energy Enhancement of the gamma-ray Strength Function of 56Fe. Physical Review C. ISSN 2469-9985. 97(2). doi: 10.1103/PhysRevC.97.024327. Full text in Research Archive Show summary

  A model-independent technique was used to determine the γ -ray strength function ( γ SF ) of 56 Fe down to γ -ray energies less than 1 MeV for the first time with GRETINA using the (p,p′ ) reaction at 16 MeV. No difference was observed in the energy dependence of the γ SF built on 2+ and 4+ final states, supporting the Brink hypothesis. In addition, angular distribution and polarization measurements were performed. The angular distributions are consistent with dipole radiation. The polarization results show a small bias towards magnetic character in the region of the enhancement.

• Larsen, Ann-Cecilie; Midtbø, Jørgen E.; Guttormsen, Magne Sveen; Renstrøm, Therese; Liddick, Sean N. & Spyrou, Artemis [Show all 22 contributors for this article] (2018). Enhanced low-energy γ-decay strength of 70Ni and its robustness within the shell model. Physical Review C. ISSN 2469-9985. 97(5), p. 1–9. doi: 10.1103/PhysRevC.97.054329. Full text in Research Archive Show summary

  Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their γ -emission probability at very low γ energies. In this work, we present measurements of the γ -decay strength of 70Ni over the wide range 1.3 Eγ 8 MeV. A significant enhancement is found in the γ -decay strength for transitions with Eγ < 3 MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed E1-strength calculations within the quasiparticle time-blocking approximation, which describe our data above Eγ 5 MeV very well. Moreover, large-scale shell-model calculations indicate an M1 nature of the low-energy γ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation, and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich 72,74,76Ni.

• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Midtbø, Jørgen E.; Campo, Lucia Crespo; Görgen, Andreas & Ingeberg, Vetle Wegner [Show all 11 contributors for this article] (2018). Gamma-widths, lifetimes and fluctuations in the nuclear quasi-continuum. The European Physical Journal Conferences. ISSN 2101-6275. 178(06001). doi: 10.1051/epjconf/201817806001. Full text in Research Archive Show summary

  Statistical γ-decay from highly excited states is determined by the nuclear level density (NLD) and the γ-ray strength function (γSF). These average quantities have been measured for several nuclei using the Oslo method. For the first time, we exploit the NLD and γSF to evaluate the γ-width in the energy region below the neutron binding energy, often called the quasi-continuum region. The lifetimes of states in the quasi-continuum are important benchmarks for a theoretical description of nuclear structure and dynamics at high temperature. The lifetimes may also have impact on reaction rates for the rapid neutron-capture process, now demonstrated to take place in neutron star mergers.

• Campo, Lucia Crespo; Guttormsen, Magne Sveen; Garrote, Frank Leonel Bello; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Show all 15 contributors for this article] (2018). Test of the generalized Brink-Axel hypothesis in 64,65Ni. Physical Review C. ISSN 2469-9985. 98, p. 054303-1–054303-10. doi: 10.1103/PhysRevC.98.054303. Full text in Research Archive Show summary

  Previously published particle-γ coincidence data on the 64Ni(p,p′γ)64Ni and 64Ni(d,pγ)65Ni reactions were further analyzed to study the statistical properties of γ decay in 64,65Ni. To do so, the γ decay to the quasicontinuum region and discrete low-lying states was investigated at γ-ray energies of 2.0–9.6 and 1.6–6.1 MeV in 64 Ni and 65 Ni, respectively. In particular, the dependence of the γ -strength function with initial and final excitation energy was studied to test the validity of the generalized Brink-Axel hypothesis. Finally, the role of fluctuations in transition strengths was estimated as a function of γ-ray and excitation energy. The γ -strength function is consistent with the hypothesis of the independence of initial excitation energy, in accordance with the generalized Brink-Axel hypothesis. The results show that the γ decay to low-lying levels displays large fluctuations for low initial excitation energies.

• Renstrøm, Therese; Utsunomiya, H.; Nyhus, Hilde-Therese; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Tveten, Gry Merete [Show all 16 contributors for this article] (2018). Verification of detailed balance for γ absorption and emission in Dy isotopes. Physical Review C. ISSN 2469-9985. 98(5), p. 1–14. doi: 10.1103/PhysRevC.98.054310. Full text in Research Archive Show summary

  The photoneutron cross sections of 162,163Dy have been measured for the first time in an energy region from the neutron threshold (Sn) up to ≈13MeV. The (γ,n) reaction was induced with quasimonochromatic laser Compton-scattered γ rays, produced at the NewSUBARU laboratory. The corresponding γ -ray strength functions (γ SF) have been calculated from the photoneutron cross sections. The data are compared to reanalyzed γSFs of 160–164Dy, which are measured below Sn. The excellent agreement with the photoneutron data at Sn confirms the principle of detailed balance. Thus, a complete γ SF is established covering in total the energy regionof1 Eγ 13MeV.Thesemid-shellwell-deformeddysprosiumisotopesallshowscissorsresonances with very similar structures. We find that our data predict the same integrated scissors strength as (γ,γ′) data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the γSFs as input in the reaction code TALYS, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined γ SFs.

• Brits, C.P.; Wiedeking, M.; Garrote, Frank Leonel Bello; Bleuel, D. L.; Giacoppo, F. & Görgen, Andreas [Show all 22 contributors for this article] (2017). Resonances in odd-odd 182Ta. The European Physical Journal Conferences. ISSN 2101-6275. 146. doi: 10.1051/epjconf/201714605012. Full text in Research Archive Show summary

  Enhanced γ -decay on the tail of the giant electric dipole resonance, such as the scissors or pygmy resonances, can have significant impact on (n,γ ) reaction rates. These rates are important input for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results from the University of Oslo indicate the existence of a significant enhancement in the photon strength function for nuclei in the actinide region due to the scissors resonance. Further, the M1 strength distribution of the scissors resonances in rare earth nuclei has been studied extensively over the years. To investigate the evolution and persistence of the scissor resonance in other mass regions, an experiment was performed utilizing the NaI(Tl) γ -ray detector array (CACTUS) and silicon particle telescopes (SiRi) at the University of Oslo Cyclotron laboratory. Particle-γ coincidences from the 181Ta(d,p)182Ta and 181Ta(d,d’)181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 181Ta and 182Ta systems, to investigate the existence of resonances below the neutron separation energy.

• Wiedeking, Mathis; Bernstein, Lee A.; Bleuel, Darren L.; Brits, Christiaan Petrus; Sowazi, Khanyisa & Görgen, Andreas [Show all 16 contributors for this article] (2017). Statistical gamma-ray decay studies at iThemba LABS. The European Physical Journal Conferences. ISSN 2101-6275. 146:05006, p. 1–4. doi: 10.1051/epjconf/201714605006. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Blasi, Nives; Bracco, Angela; Camera, Franco & Campo, Lucia Crespo [Show all 24 contributors for this article] (2017). Low-energy enhancement and fluctuations of γ-ray strength functions in 56,57Fe: test of the Brink–Axel hypothesis. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 44(6). doi: 10.1088/1361-6471/aa644a. Full text in Research Archive Show summary

  Nuclear level densities and γ-ray strength functions of 56,57Fe have been extracted from proton-γ coincidences. A low-energy enhancement in the γ-ray strength functions up to a factor of 30 over common theoretical E1 models is confirmed. Angular distributions of the low-energy enhancement in 57Fe indicate its dipole nature, in agreement with findings for 56Fe. The high statistics and the excellent energy resolution of the large-volume LaBr3(Ce) detectors allowed for a thorough analysis of γ strength as function of excitation energy. Taking into account the presence of strong Porter–Thomas fluctuations, there is no indication of any significant excitation energy dependence in the γ-ray strength function, in support of the generalized Brink–Axel hypothesis. This research was first published in Journal of Physics G: Nuclear and Particle Physics. © IOP Publishing.

• Malatji, Kgashane L.; Kheswa, Bonginkosi Vincent; Wiedeking, M.; Garrote, Frank Leonel Bello; Brits, C.P. & Bleuel, D. L. [Show all 21 contributors for this article] (2017). Nuclear level densities and γ-ray strength functions of 180,181Ta and neutron capture cross sections. The European Physical Journal Conferences. ISSN 2101-6275. 146. doi: 10.1051/epjconf/201714601010. Full text in Research Archive Show summary

  The γ -ray strength functions and nuclear level densities in the quasi-continuum of 180,181Ta are extracted from particle-γ coincidence events with the Oslo Method, below the Sn . The data were used as input in the TALYS reaction code for calculations of the astrophysical Maxwellian-averaged (n, γ ) cross-sections to investigate nucleosynthesis of nature’s rarest stable isotope 180Ta.

• Guttormsen, Magne Sveen; Goriely, Stephan; Larsen, Ann-Cecilie; Görgen, Andreas; Hagen, Trine Wiborg & Renstrøm, Therese [Show all 13 contributors for this article] (2017). Quasicontinuum γ decay of 91,92Zr: Benchmarking indirect (n,γ ) cross section measurements for the s process. Physical Review C. ISSN 2469-9985. 96(2). doi: 10.1103/PhysRevC.96.024313. Full text in Research Archive Show summary

  Nuclear level densities (NLDs) and γ-ray strength functions (γSFs) have been extracted from particle-γ coincidences of the 92Zr(p,p′γ)92Zr and 92Zr(p,dγ)91Zr reactions using the Oslo method. The new 91,92ZrγSF data, combined with photonuclear cross sections, cover the whole energy range from Eγ≈1.5MeV up to the giant dipole resonance at Eγ≈17 MeV. The wide-range γSF data display structures at Eγ≈9.5 MeV, compatible with a superposition of the spin-flip M1 resonance and a pygmy E1 resonance. Furthermore, the γSF shows a minimum at Eγ≈2–3MeV and an increase at lower γ-ray energies. The experimentally constrained NLDs and γSFs are shown to reproduce known (n,γ) and Maxwellian-averaged cross sections for 91,92Zr using the talys reaction code, thus serving as a benchmark for this indirect method of estimating (n,γ) cross sections for Zr isotopes. This research was originally published in Physical Review C - Nuclear Physics. © American Physical Society

• Jurado, B; Marini, P; Mathieu, L; Aiche, M; Czajkowski, S & Tsekhanovich, I [Show all 19 contributors for this article] (2017). Investigation of the surrogate-reaction method via the simultaneous measurement of gamma-emission and fission probabilities. The European Physical Journal Conferences. ISSN 2101-6275. 146. doi: 10.1051/epjconf/201714611006. Full text in Research Archive
• Rose, Sunniva Johanne; Zeiser, Fabio; Wilson, JN; Oberstedt, A; Oberstedt, S & Siem, Sunniva [Show all 25 contributors for this article] (2017). Energy dependence of the prompt gamma-ray emission from the (d,p)-induced fission of U-234 and Pu-240. Physical Review C. ISSN 2469-9985. 96(1). doi: 10.1103/PhysRevC.96.014601. Full text in Research Archive Show summary

  Prompt-fission γ rays are responsible for approximately 5% of the total energy released in fission, and therefore important to understand when modeling nuclear reactors. In this work we present prompt γ -ray emission characteristics in fission as a function of the nuclear excitation energy of the fissioning system. Emitted γ -ray spectra were measured, and γ -ray multiplicities and average and total γ energies per fission were determined for the 233 U ( d , p f ) reaction for excitation energies between 4.8 and 10 MeV, and for the 239 Pu ( d , p f ) reaction between 4.5 and 9 MeV. The spectral characteristics show no significant change as a function of excitation energy above the fission barrier, despite the fact that an extra ∼ 5 MeV of energy is potentially available in the excited fragments for γ decay. The measured results are compared with model calculations made for prompt γ -ray emission with the fission model code gef. Further comparison with previously obtained results from thermal neutron induced fission is made to characterize possible differences arising from using the surrogate ( d , p ) reaction.

• Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 23 contributors for this article] (2017). The Statistical Properties Of 92Mo And Implications For The p-process. Proceedings of Science (PoS). INPC2016. Full text in Research Archive Show summary

  A particularly challenging part of the question of how elements heavier than iron are created in extreme, astrophysical environments is the creation of the so-called p-nuclei, which are believed to be mainly produced in the O-Ne layer of type II supernovae or type Ia supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions for the production of these isotopes. Astrophysical model calculations are able to reproduce abundance patterns of most p-isotopes reasonably well, with some pivotal exceptions. In particular, p-isotopes of mass 92 ≤ A ≤ 98 are underproduced in calculations compared to the actual abundance of these isotopes. The p-isotope 92Mo represents one of the most severe cases of underproduction. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. The main destruction mechanism of this isotope in the standard description of the p-process is through the 92Mo(γ, p)91Nb reaction. Measurements on the nuclear level density and average gamma strength function of 92Mo have been carried out at the Oslo Cyclotron Laboratory. TALYS cross section and reaction rate calculations where the experimental results are used as input will be presented. The data provide stringent constraints on the 91Nb(p, γ)92Mo (and consequently the inverse) reaction rate. The reaction rate extracted in this work was used in reaction network calculations for the scenario of a p-process taking place in a type II supernova explosion as the shock front passes through the O-Ne layer of a 25 solar mass star.

• Campo, Lucia Crespo; Larsen, Ann-Cecilie; Garrote, Frank Leonel Bello; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Show all 13 contributors for this article] (2017). Investigating the gamma decay of Ni 65 from particle-gamma coincidence data. Physical Review C. ISSN 2469-9985. 96(1). doi: 10.1103/PhysRevC.96.014312. Full text in Research Archive Show summary

  The γ decay of 65 Ni has been studied from particle- γ coincidence data on the 64 Ni ( d , p γ ) 65 Ni reaction. γ -ray spectra at excitation energies below Ex≈ 2 MeV have been studied and compared with previous measurements. Coincidences corresponding to Ex≈ 4.4 – 6.1 MeV have been used to constrain the shape of the nuclear level density and γ -strength function of 65 Ni by means of the Oslo method. The experimental γ -strength function presents an enhancement at γ energies below Eγ ≈ 3 MeV . In addition, a resonance-like structure centered at Eγ ≈ 4.6 MeV is seen together with accumulated strength at Eγ ≈ 2.6 – 3.6 MeV . The obtained results contribute to the systematic study of γ decay in the Ni isotopes, which is of great interest for the understanding of both single-particle and collective nuclear structure phenomena.

• Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Brown, Joshua A.; Larsen, Ann-Cecilie; Goriely, Stéphane & Guttormsen, Magne Sveen [Show all 25 contributors for this article] (2017). 137,138,139La(n,γ) cross sections constrained with statistical decay properties of 138,139,140La nuclei. Physical Review C. ISSN 2469-9985. 95(4). doi: 10.1103/PhysRevC.95.045805. Full text in Research Archive Show summary

  The nuclear level densities and γ-ray strength functions of 138,139,140La were measured using the 139La(3He,α), 139La(3He,'3He), and 139La(d,p) reactions. The particle-γ coincidences were recorded with the silicon particle telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these experimental results, the low-energy enhancement in the A∼140 region is discussed. The 137,138,139La(n,γ) cross sections were calculated at s- and p-process temperatures using the experimentally measured nuclear level densities and γ-ray strength functions. Good agreement is found between 139La(n,γ) calculated cross sections and previous measurements. This research was first published in Physical Review C - Nuclear Physics. © American Physical Society.

• Larsen, Ann-Cecilie; Spyrou, Artemis; Liddick, Sean N.; Guttormsen, Magne Sveen; Ingeberg, Vetle Wegner & Siem, Sunniva [Show all 25 contributors for this article] (2017). Novel Techniques for Constraining Neutron-capture Rates relevant to Heavy-element Nucleosynthesis. Proceedings of Science (PoS). INPC2016. doi: 10.22323/1.281.0360. Full text in Research Archive Show summary

  In this contribution we discuss new experimental approaches to indirectly provide information on neutron-capture rates relevant to the r-process. In particular, we focus on applications of the Oslo method to extract fundamental nuclear properties for reaction-rate calculations: the nuclear level density and the γ strength function. Two methods are discussed in detail, the Oslo method in inverse kinematics and the beta-Oslo method. These methods present a first step towards constraining neutron-capture rates of importance to the r-process.

• Spyrou, Artemis; Larsen, Ann-Cecilie; Liddick, Sean N.; Naqvi, Farheen; Crider, Benjamin P. & Dombos, Alexander C. [Show all 19 contributors for this article] (2017). Neutron-capture rates for explosive nucleosynthesis: the case of 68Ni(n, γ)69Ni. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 44. doi: 10.1088/1361-6471/aa5ae7. Full text in Research Archive Show summary

  Neutron-capture reactions play an important role in heavy element nucleosynthesis, since they are the driving force for the two processes that create the vast majority of the heavy elements. When a neutron capture occurs on a short-lived nucleus, it is extremely challenging to study the reaction directly and therefore the use of indirect techniques is essential. The present work reports on such an indirect measurement that provides strong constraints on the 68Ni(n, γ)69Ni reaction rate. This is done by populating the compound nucleus 69Ni via the β decay of 69Co and measuring the γ-ray deexcitation of excited states in 69Ni. The β-Oslo method was used to extract the γ-ray strength function and the nuclear level density. In addition the half-life of 69Co was extracted and found to be in agreement with previous literature values. Before the present results, the 68Ni(n, γ)69Ni reaction was unconstrained and the purely theoretical reaction rate was highly uncertain. The new uncertainty on the reaction rate based on the present experiment (variation between upper and lower limit) is approximately a factor of 3. The commonly used reaction libraries JINA-REACLIB and BRUSLIB are in relatively good agreement with the experimental rate. The impact of the new rate on weak r-process calculations is discussed. This research was first published in Journal of Physics G: Nuclear and Particle Physics. © IOP Publishing.

• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Görgen, Andreas; Renstrøm, Therese; Siem, Sunniva & Tornyi, Tamas Gabor [Show all 7 contributors for this article] (2016). Is the generalized Brink-Axel hypothesis valid? Proceedings of Science (PoS). 2016-September, p. 1–8. doi: 10.22323/1.281.0062. Full text in Research Archive Show summary

  Experimental results of the 237Np(d, pγ) 238Np reaction are presented, which verifies the generalized Brink-Axel (gBA) hypothesis for γ transitions between states in the quasi-continuum. The gBA hypothesis holds not only for specific collective resonances, but for the full dipole strength below the neutron separation energy. We discuss the validity of the gBA hypothesis also for lighter systems like 92Zr where the concept of a unique γ-ray strength function (γSF) is problematic due to large Porter-Thomas fluctuations. Methods for studying the γSF and the fluctuations as function of excitation energy are presented.

• Campo, Lucia Crespo; Garrote, Frank Leonel Bello; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen & Hadynska-Klek, Katarzyna [Show all 14 contributors for this article] (2016). Statistical γ -decay properties of Ni 64 and deduced (n,γ) cross section of the s -process branch-point nucleus Ni 63. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(4). doi: 10.1103/PhysRevC.94.044321. Full text in Research Archive Show summary

  Particle-γ coincidence data have been analyzed to obtain the nuclear level density and the γ -strength function of 64Ni by means of the Oslo method. The level density found in this work is in very good agreement with known energy levels at low excitation energies as well as with data deduced from particle-evaporation measurements at excitation energies above Ex ≈ 5.5 MeV. The experimental γ -strength function presents an enhancement at γ energies below Eγ ≈ 3 MeV and possibly a resonancelike structure centered at Eγ ≈ 9.2 MeV. The obtained nuclear level density and γ -strength function have been used to estimate the (n,γ ) cross section for the s-process branch-point nucleus 63Ni, of particular interest for astrophysical calculations of elemental abundances.

• Ay, K.o.; Ozgur, Mustafa; Algin, Emel; Guttormsen, Magne Sveen; Garrote, Frank Leonel Bello & Campo, Lucia Crespo [Show all 20 contributors for this article] (2016). Nuclear level densities and gamma-ray strength functions of 145,149,151Nd isotopes. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 766(012027). doi: 10.1088/1742-6596/766/1/012027. Full text in Research Archive
• Marini, P.; Ducasse, Q; Jurado, B; Aiche, M; Mathieu, L & Barreau, G. [Show all 33 contributors for this article] (2016). First simultaneous measurement of fission and gamma probabilities of &lt;sup&gt;237&lt;/sup&gt;U and &lt;sup&gt;239&lt;/sup&gt;Np via surrogate reactions. The European Physical Journal Conferences. ISSN 2101-6275. 122. doi: 10.1051/epjconf/201612212004. Full text in Research Archive
• Spyrou, Artemis; Liddick, Sean N.; Naqvi, Farheen; Crider, Benjamin P.; Dombos, Alexander C. & Bleuel, Darren L. [Show all 21 contributors for this article] (2016). Strong Neutron-γ Competition above the Neutron Threshold in the Decay of 70Co. Physical Review Letters. ISSN 0031-9007. 117(14). doi: 10.1103/PhysRevLett.117.142701. Full text in Research Archive Show summary

  The β-decay intensity of 70Co was measured for the first time using the technique of total absorption spectroscopy. The large β-decay Q value [12.3(3) MeV] offers a rare opportunity to study β-decay properties in a broad energy range. Two surprising features were observed in the experimental results, namely, the large fragmentation of the β intensity at high energies, as well as the strong competition between γ rays and neutrons, up to more than 2 MeV above the neutron-separation energy. The data are compared to two theoretical calculations: the shell model and the quasiparticle random phase approximation (QRPA). Both models seem to be missing a significant strength at high excitation energies. Possible interpretations of this discrepancy are discussed. The shell model is used for a detailed nuclear structure interpretation and helps to explain the observed γ-neutron competition. The comparison to the QRPA calculations is done as a means to test a model that provides global β-decay properties for astrophysical calculations. Our work demonstrates the importance of performing detailed comparisons to experimental results, beyond the simple half-life comparisons. A realistic and robust description of the β-decay intensity is crucial for our understanding of nuclear structure as well as of r-process nucleosynthesis.

• Larsen, Ann-Cecilie; Spyrou, Artemisia; Liddick, Sean N.; Guttormsen, Magne Sveen; Ingeberg, Vetle Wegner & Siem, Sunniva [Show all 25 contributors for this article] (2016). Novel techniques for constraining neutron-capture rates relevant to heavy-element nucleosynthesis. Proceedings of Science (PoS). 2016-September:360, p. 1–9. Full text in Research Archive Show summary

  In this contribution we discuss new experimental approaches to indirectly provide information on neutron-capture rates relevant to the r-process. In particular, we focus on applications of the Oslo method to extract fundamental nuclear properties for reaction-rate calculations: the nuclear level density and the γ strength function. Two methods are discussed in detail, the Oslo method in inverse kinematics and the beta-Oslo method. These methods present a first step towards constraining neutron-capture rates of importance to the r-process.

• Laplace, Thibault A.; Zeiser, Fabio; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bleuel, Darren L. & Bernstein, Lee A. [Show all 27 contributors for this article] (2016). Statistical properties of Pu 243, and Pu 242 (n,γ) cross section calculation. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(1). doi: 10.1103/PhysRevC.93.014323. Full text in Research Archive Show summary

  The level density and γ -ray strength function (γ SF) of 243Pu have been measured in the quasicontinuum using the Oslo method. Excited states in 243Pu were populated using the 242Pu(d,p) reaction. The level density closely follows the constant-temperature level density formula for excitation energies above the pairing gap. The γ SF displays a double-humped resonance at low energy as also seen in previous investigations of actinide isotopes. The structure is interpreted as the scissors resonance and has a centroid of ωSR = 2.42(5) MeV and a total strength of BSR = 10.1(15) μ2 N , which is in excellent agreement with sum-rule estimates. The measured level density and γ SF were used to calculate the 242Pu(n,γ ) cross section in a neutron energy range for which there were previously no measured data.

• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Görgen, Andreas; Renstrøm, Therese; Siem, Sunniva & Tornyi, Tamas Gabor [Show all 7 contributors for this article] (2016). Validity of the Generalized Brink-Axel Hypothesis in Np 238. Physical Review Letters. ISSN 0031-9007. 116(1). doi: 10.1103/PhysRevLett.116.012502. Full text in Research Archive Show summary

  We analyze primary γ-ray spectra of the odd-odd 238Np nucleus extracted from 237Npðd; pγÞ238Np coincidence data measured at the Oslo Cyclotron Laboratory. The primary γ spectra cover an excitationenergy region of 0 ≤ Ei ≤ 5.4 MeV, and allow us to perform a detailed study of the γ-ray strength as a function of excitation energy. Hence, we can test the validity of the generalized Brink-Axel hypothesis, which, in its strictest form, claims no excitation-energy dependence on the γ strength. In this work, using the available high-quality 238Np data, we show that the γ-ray strength function is to a very large extent independent of the initial and final states. Thus, for the first time, the generalized Brink-Axel hypothesis is experimentally verified for γ transitions between states in the quasicontinuum region, not only for specific collective resonances, but also for the full strength below the neutron separation energy. Based on our findings, the necessary criteria for the generalized Brink-Axel hypothesis to be fulfilled are outlined.

• Liddick, Sean N.; Spyrou, Artemisia; Crider, Benjamin P.; Naqvi, Farheen; Larsen, Ann-Cecilie & Guttormsen, Magne Sveen [Show all 21 contributors for this article] (2016). Experimental Neutron Capture Rate Constraint Far from Stability. Physical Review Letters. ISSN 0031-9007. 116:242502(24). doi: 10.1103/PhysRevLett.116.242502. Full text in Research Archive Show summary

  Nuclear reactions where an exotic nucleus captures a neutron are critical for a wide variety of applications, from energy production and national security, to astrophysical processes, and nucleosynthesis. Neutron capture rates are well constrained near stable isotopes where experimental data are available; however, moving far from the valley of stability, uncertainties grow by orders of magnitude. This is due to the complete lack of experimental constraints, as the direct measurement of a neutron-capture reaction on a short-lived nucleus is extremely challenging. Here, we report on the first experimental extraction of a neutron capture reaction rate on 69 Ni , a nucleus that is five neutrons away from the last stable isotope of Ni. The implications of this measurement on nucleosynthesis around mass 70 are discussed, and the impact of similar future measurements on the understanding of the origin of the heavy elements in the cosmos is presented.

• Renstrøm, Therese; Nyhus, Hilde-Therese; Utsunomiya, Hiroaki; Schwengner, Ronald; Goriely, Stephane & Larsen, Ann-Cecilie [Show all 25 contributors for this article] (2016). Low-energy enhancement in the γ-ray strength functions of Ge73,74. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(6). doi: 10.1103/PhysRevC.93.064302. Full text in Research Archive Show summary

  The γ -ray strength functions and level densities of 73,74Ge have been extracted up to the neutron-separation energy Sn from particle-γ coincidence data using the Oslo method. Moreover, the γ -ray strength function of 74Ge above Sn has been determined from photoneutron measurements; hence these two experiments cover the range of Eγ ≈ 1–13 MeV for 74Ge. The obtained data show that both 73,74Ge display an increase in strength at low γ energies. The experimental γ -ray strength functions are compared with M1 strength functions deduced from average B(M1) values calculated within the shell model for a large number of transitions. The observed low-energy enhancements in 73,74Ge are adopted in the calculations of the 72,73Ge(n,γ ) cross sections, where there are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes are shown to be strongly dependent on the presence of the low-energy enhancement.

• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Schwengner, Ronald; Bleuel, Darren L.; Goriely, Stephane & Harrisopulos, Sotirios [Show all 21 contributors for this article] (2016). Experimentally constrained (p,γ) y 89 and (n,γ) y 89 reaction rates relevant to p -process nucleosynthesis. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(4). doi: 10.1103/PhysRevC.93.045810. Full text in Research Archive Show summary

  The nuclear level density and the γ -ray strength function have been extracted for 89Y by using the Oslo method on 89Y(p,p γ ) 89Y coincidence data. The γ -ray strength function displays a low-energy enhancement consistent with previous observations in this mass region (93–98Mo). Shell-model calculations support the conclusion that the observed enhancement is due to strong, low-energy M1 transitions at high excitation energies. The data were further used as input for calculations of the 88Sr(p,γ ) 89Y and 88Y(n,γ ) 89Y cross sections with the TALYS reaction code. Comparison with cross-section data, where available, as well as with values from the BRUSLIB library, shows a satisfying agreement.

• Ducasse, Q; Jurado, B; Aiche, M; Marini, P; Mathieu, L & Görgen, Andreas [Show all 29 contributors for this article] (2016). Investigation of the U 238 (d,p) surrogate reaction via the simultaneous measurement of γ -decay and fission probabilities. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(2). doi: 10.1103/PhysRevC.94.024614. Full text in Research Archive Show summary

  We investigated the 238U(d,p) reaction as a surrogate for the n + 238U reaction. For this purpose we measured for the first time the γ -decay and fission probabilities of 239U∗ simultaneously and compared them to the corresponding neutron-induced data. We present the details of the procedure to infer the decay probabilities, as well as a thorough uncertainty analysis, including parameter correlations. Calculations based on the continuumdiscretized coupled-channels method and the distorted-wave Born approximation (DWBA) were used to correct our data from detected protons originating from elastic and inelastic deuteron breakup. In the region where fission and γ emission compete, the corrected fission probability is in agreement with neutron-induced data, whereas the γ -decay probability is much higher than the neutron-induced data. We have performed calculations of the decay probabilities with the statistical model and of the average angular momentum populated in the 238U(d,p) reaction with the DWBA to interpret these results.

• Negi, D; Wiedeking, M; Lanza, EG; Litvinova, E; Vitturi, A & Bark, RA [Show all 35 contributors for this article] (2016). Nature of low-lying electric dipole resonance excitations in Ge 74. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(2). doi: 10.1103/PhysRevC.94.024332. Full text in Research Archive Show summary

  Isospin properties of dipole excitations in 74 Ge are investigated using the (α , α ′ γ ) reaction and compared to (γ , γ ′ ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy, being populated by both isoscalar and isovector probes, and the other at high energy, excited only by the electromagnetic probe. Relativistic quasiparticle time blocking approximation (RQTBA) calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy, which is consistent with the measurement.

• Tveten, Gry Merete; Spyrou, A; Schwengner, R; Naqvi, F; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 23 contributors for this article] (2016). Completing the nuclear reaction puzzle of the nucleosynthesis of Mo 92. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(2). doi: 10.1103/PhysRevC.94.025804. Full text in Research Archive Show summary

  One of the greatest questions for modern physics to address is how elements heavier than iron are created in extreme astrophysical environments. A particularly challenging part of that question is the creation of the so-called p-nuclei, which are believed to be mainly produced in some types of supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions. In this work, we present for the first time measurements on the nuclear level density and average γ strength function of 92Mo. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. Our data provide stringent constraints on the 91Nb(p,γ ) 92Mo reaction rate, which is the last unmeasured reaction in the nucleosynthesis puzzle of 92Mo. Based on our results, we conclude that the 92Mo abundance anomaly is not due to the nuclear physics input to astrophysical model calculations.

• Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 23 contributors for this article] (2016). The statistical properties of 92Mo and implications for the p-process. Proceedings of Science (PoS). 2016-September:163. Full text in Research Archive
• Simon, Anna; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Beausang, Con W.; Humby, Peter & Burke, Jason T. [Show all 17 contributors for this article] (2016). First observation of low-energy γ -ray enhancement in the rare-earth region. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93:034303. doi: 10.1103/PhysRevC.93.034303. Full text in Research Archive Show summary

  The γ -ray strength function and level density in the quasi-continuum of 151,153Sm have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the γ strength down to unprecedentedly low γ energies of ≈500 keV. For the first time an enhanced low-energy γ -ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low γ energies could have an impact of 2–3 orders of magnitude on the (n,γ ) reaction rates for r-process nucleosynthesis.

• Moretto, Luciano; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Siem, Sunniva (2015). The little hagedorn that could. Proceedings of Science (PoS). 26-30-January-2015:058. Full text in Research Archive Show summary

  The Hagedorn exponential mass spectrum with slope 1/TH was erroneously interpreted as fixing an upper limiting temperature TH that the system can achieve. To the contrary, such spectrum indicates a 1st order phase transition at a fixed temperature TH. A much lower energy example is the log linear level nuclear density below the neutron binding energy that prevails throughout the nuclear chart. We show that, for non-magic nuclei, such linearity implies a 1st order phase transition from the pairing superfluid to an ideal gas of quasi particles.

• Giacoppo, Francesca; Garrote, Frank Leonel Bello; Bernstein, Lee; Bleuel, D.l.; Firestone, R.B. & Görgen, Andreas [Show all 16 contributors for this article] (2015). Gamma decay from the quasicontinuum of 197,198Au. Physical Review C. Nuclear Physics. ISSN 0556-2813. 91. doi: 10.1103/PhysRevC.91.054327. Full text in Research Archive Show summary

  The average electromagnetic dipole response of levels in the quasicontinuum of 197,198Au has been measured using (3He,3He ) and (d,p) reactions. The extracted γ -ray strength functions have been normalized according to three model assumptions for the nuclear spin distribution. An enhancement in the energy region Eγ = 3.0–6.5 MeV is observed for both isotopes. The E1 component of such excess of strength is studied in detail for 198Au and is interpreted as the pygmy dipole resonance with an energy centroid of 5.9(1) MeV and exhausts about 1% of the total integrated strength. The pygmy dipole resonance is shown to have a significant impact on the calculated 197Au(n,γ ) 198Au cross section.

• Larsen, Ann-Cecilie; Goriely, Stephane; Bernstein, L. A.; Bleuel, D. L.; Bracco, A. & Brown, B. A. [Show all 25 contributors for this article] (2015). Upbend and M1 scissors mode in neutron-rich nuclei — consequences for r-process (n,gamma) reaction rates. Acta Physica Polonica B. ISSN 0587-4254. 46(3), p. 509–512. doi: 10.5506/APhysPolB.46.509. Full text in Research Archive Show summary

  An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. The experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

• Tveten, Gry Merete; Garrote, Frank Leonel Bello; Campo, Lucia Crespo; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Guttormsen, Magne Sveen [Show all 18 contributors for this article] (2015). The statistical properties of 111,112,113Sn studied with the Oslo method. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159304004. Full text in Research Archive Show summary

  The γ-ray strength function and level density of 111, 112, 113Sn are being studied at the Oslo Cyclotron Laboratory (OCL) up to the neutron binding energy by applying the Oslo method to particle-γ coincidence data. The preliminary results for the γ-ray strength function are discussed in the context of the results for the more neutron-rich Sn-isotopes previously studied at OCL.

• Guttormsen, Magne Sveen; Aiche, M; Garrote, Frank Leonel Bello; Bernstein, Lee; Bleuel, D.l. & Byun, Y. [Show all 27 contributors for this article] (2015). Experimental level densities of atomic nuclei. European Physical Journal A. ISSN 1434-6001. 51(12), p. 1–8. doi: 10.1140/epja/i2015-15170-4. Full text in Research Archive
• Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Giacoppo, Francesca; Goriely, Stephan; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 19 contributors for this article] (2015). Galactic production of 138La: Impact of 138,139La statistical properties. Physics Letters B. ISSN 0370-2693. 744, p. 268–272. doi: 10.1016/j.physletb.2015.03.065. Full text in Research Archive Show summary

  The γ-ray strength functions and nuclear level densities of 138La and 139La have been measured below the neutron separation energies. These new data were used to calculate astrophysical Maxwellian-averaged () cross-sections to investigate the production and destruction of the p-nucleus 138La in the photodisintegration process. The results confirm the underproduction of 138La in the p-process with respect to the observed abundances and strongly support the ν-process through capture on 138Ba as the main contributor to the synthesis of 138La in Type II supernovae.

• Moretto, L.G.; Larsen, Ann-Cecilie; Giacoppo, Francesca; Guttormsen, Magne Sveen & Siem, Sunniva (2015). Experimental first order pairing phase transition in atomic nuclei. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 580:012048, p. 1–7. doi: 10.1088/1742-6596/580/1/012048. Full text in Research Archive Show summary

  The natural log of experimental nuclear level densities at low energy is linear with energy. This can be interpreted in terms of a nearly 1st order phase transition from a superfluid to an ideal gas of quasi particles. The transition temperature coincides with the BCS critical temperature and yields gap parameters in good agreement with the values extracted from even- odd mass differences from rotational states. This converging evidence supports the relevance of the BCS theory to atomic nuclei.

• Renstrøm, Therese; Nyhus, Hilde-Therese; Utsunomiya, Hiroaki; Larsen, Ann-Cecilie; Siem, Sunniva & Guttormsen, Magne Sveen [Show all 25 contributors for this article] (2015). First evidence of low energy enhancement in Ge isotopes. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159304003. Full text in Research Archive Show summary

  The γ-strength functions and level densities of 73,74Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ∼1-13 MeV for 74Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ∼3 MeV towards lower γ energies. The obtained data show that both 73,74Ge display an increase in strength at low γ energies.

• Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Giacoppo, Francesca; Goriely, Stephane; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 19 contributors for this article] (2015). Statistical nuclear properties and synthesis of La-138. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159304005. Full text in Research Archive
• Giacoppo, Francesca; Garrote, Frank Leonel Bello; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen & Hagen, Trine Wiborg [Show all 16 contributors for this article] (2015). Observation of low-lying resonances in the quasicontinuum of Pt-195,Pt-196 and enhanced astrophysical reaction rates. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159301039. Full text in Research Archive
• Tornyi, Tamas Gabor; Görgen, Andreas; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Siem, Sunniva & Krasznahorkay, Attila [Show all 7 contributors for this article] (2014). A new fission-fragment detector to complement the CACTUS-SiRi setup at the Oslo Cyclotron Laboratory. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 738, p. 6–12. doi: 10.1016/j.nima.2013.12.005. Full text in Research Archive
• Guttormsen, Magne Sveen; Bernstein, Lee; Görgen, Andreas; Jurado, Beatriz; Siem, Sunniva & Aiche, M [Show all 19 contributors for this article] (2014). Scissors resonance in the quasicontinuum of Th, Pa, and U isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 89(014302). doi: 10.1103/PhysRevC.89.014302. Full text in Research Archive
• Spyrou, A.; Liddick, S.N.; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Cooper, K. & Dombos, A.C. [Show all 15 contributors for this article] (2014). Novel technique for Constraining r-Process (n, γ) Reaction Rates. Physical Review Letters. ISSN 0031-9007. 113(232502). doi: 10.1103/PhysRevLett.113.232502. Full text in Research Archive Show summary

  A novel technique has been developed, which will open exciting new opportunities for studying the very neutron-rich nuclei involved in the r process. As a proof of principle, the γ spectra from the β decay of 76Ga have been measured with the SuN detector at the National Superconducting Cyclotron Laboratory. The nuclear level density and γ-ray strength function are extracted and used as input to Hauser-Feshbach calculations. The present technique is shown to strongly constrain the 75Ge(n,γ)76Ge cross section and reaction rate. © 2014 American Physical Society

• Eriksen, Tomas Kvalheim; Nyhus, Hilde-Therese; Guttormsen, Magne Sveen; Görgen, Andreas; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 11 contributors for this article] (2014). Pygmy resonance and low-energy enhancement in the γ-ray strength functions of Pd isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 90(044311). doi: 10.1103/PhysRevC.90.044311. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Garrote, Frank Leonel Bello; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Show all 16 contributors for this article] (2014). Shell-gap-reduced level densities in 89,90Y. Physical Review C. Nuclear Physics. ISSN 0556-2813. 90(044309). doi: 10.1103/PhysRevC.90.044309. Full text in Research Archive
• Giacoppo, Francesca; Garrote, Frank Leonel Bello; Bernstein, Lee A.; Bleuel, Darren L.; Firestone, Richard & Görgen, Andreas [Show all 16 contributors for this article] (2014). Statistical gamma-ray emission of gold and its astrophysical implications. The European Physical Journal Conferences. ISSN 2101-6275. 66:02041. doi: 10.1051/epjconf/20146602041. Full text in Research Archive
• Giacoppo, Francesca; Garrote, Frank Leonel Bello; Bernstein, L. A.; Bleuel, D. L.; Eriksen, Tomas Kvalheim & Firestone, Richard [Show all 18 contributors for this article] (2014). Level densities and thermodynamical properties of Pt and Au isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 90(5). doi: 10.1103/PhysRevC.90.054330. Full text in Research Archive Show summary

  The nuclear level densities of 194–196Pt and 197,198Au below the neutron separation energy have been measured using transfer and scattering reactions. All the level density distributions follow the constant-temperature description. Each group of isotopes is characterized by the same temperature above the energy threshold corresponding to the breaking of the first Cooper pair. A constant entropy excess ΔS=1.9kB and 1.1kB is observed in 195Pt and 198Au with respect to 196Pt and 197Au, respectively, giving information on the available single-particle level space for the last unpaired valence neutron. The breaking of nucleon Cooper pairs is revealed by sequential peaks in the microcanonical caloric curve. © 2014 American Physical Society

• Krzysiek, M; Bürger, Alexander; Görgen, Andreas; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Siem, Sunniva [Show all 53 contributors for this article] (2014). Study of the soft dipole modes in 140Ce via inelastic scattering of 17O. Physica Scripta. ISSN 0031-8949. 89(5). doi: 10.1088/0031-8949/89/5/054016. Full text in Research Archive
• Tornyi, Tamas Gabor; Guttormsen, Magne Sveen; Eriksen, Tomas Kvalheim; Görgen, Andreas; Giacoppo, Francesca & Hagen, Trine Wiborg [Show all 12 contributors for this article] (2014). Level density and gamma-ray strength function in the odd-odd 238Np nucleus. Physical Review C. Nuclear Physics. ISSN 0556-2813. 89(4). doi: 10.1103/PhysRevC.89.044323. Full text in Research Archive
• Guttormsen, Magne Sveen; Bernstein, L. A.; Bürger, Alexander; Görgen, Andreas; Gunsing, F. & Hagen, Trine Wiborg [Show all 11 contributors for this article] (2014). Scissors strength in the quasi-continuum of actinides. The European Physical Journal Conferences. ISSN 2101-6275. 66. doi: 10.1051/epjconf/20146602044. Full text in Research Archive
• Bree, Nick; Wrzosek-Lipska, K; Petts, A; Andreyev, A; Bastin, B & Bender, M [Show all 70 contributors for this article] (2014). Shape coexistence in the neutron-deficient even-even hg 182-188 isotopes studied via coulomb excitation. Physical Review Letters. ISSN 0031-9007. 112:162701(16). doi: 10.1103/PhysRevLett.112.162701. Full text in Research Archive
• Ducasse, Quentin; Jurado, Beatriz; Tornyi, Tamas Gabor; Görgen, Andreas; Wilson, J.D. & Giacoppo, Francesca [Show all 28 contributors for this article] (2014). Neutron-induced Cross Sections of Actinides via the Surrogate-reaction Method. Nuclear Data Sheets. ISSN 0090-3752. 119, p. 233–233. doi: 10.1016/j.nds.2014.08.064. Full text in Research Archive
• Voinov, A.V.; Grimes, S.M.; Brune, C.R.; Bürger, Alexander; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 9 contributors for this article] (2014). Level Density Inputs in Nuclear Reaction Codes and the Role of the Spin Cutoff Parameter. Nuclear Data Sheets. ISSN 0090-3752. 119, p. 255–255. doi: 10.1016/j.nds.2014.08.070. Full text in Research Archive
• Larsen, Ann-Cecilie; Blasi, Nives; Bracco, Angela; Bürger, Arnold; Camera, Franco & Eriksen, Tomas Kvalheim [Show all 25 contributors for this article] (2014). Low-energy enhancement of nuclear γ strength and its impact on astrophysical reaction rates. The European Physical Journal Conferences. ISSN 2101-6275. doi: 10.1051/epjconf/20146607014. Full text in Research Archive Show summary

  An unexpected enhancement in the low-energy part of the γ-strength function for light and medium-mass nuclei has been discovered at the Oslo Cyclotron Laboratory. This enhancement could lead to an increase in the neutron-capture rates up to two orders of magnitude for very exotic, neutron-rich nuclei. However, it is still an open question whether this structure persists when approaching the neutron drip line.

• Utsunomiya, H.; Goriely, Stephane; Kondo, T.; Iwamoto, C.; Akimune, H. & Yamagata, T. [Show all 17 contributors for this article] (2013). Photoneutron cross sections for Mo isotopes: A step toward a unified understanding of (gamma,n) and (n,gamma) reactions. Physical Review C. Nuclear Physics. ISSN 0556-2813. 88(1). doi: 10.1103/PhysRevC.88.015805. Full text in Research Archive Show summary

  Photoneutron cross sections were measured for 94Mo, 95Mo, 96Mo, 97Mo, 98Mo, and 100Mo near the neutron threshold with quasi-monochromatic laser-Compton scattering γ rays. The photoneutron data were analyzed with the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric-deformed Gogny HFB plus QRPA model of E1 γ-ray strength. Combining the γ-ray strength function constrained by the present photoneutron data with either the nuclear resonance fluorescence data or the updated Oslo data to supplement the data below the neutron threshold, a thorough analysis of the reverse (n,γ) cross sections is made whenever measurements are available. The Oslo data and the corresponding uncertainties are updated based on the latest results of the s-wave neutron spacing and the average radiative width determined in particular for 96Mo. Finally, radiative neutron capture cross sections for two radioactive nuclei, 93Mo and 99Mo, are deduced with the γ-ray strength function method. © 2013 American Physical Society

• Larsen, Ann-Cecilie; Blasi, Nives; Bracco, Angela; Camera, Franco; Eriksen, Tomas Kvalheim & Görgen, Andreas [Show all 19 contributors for this article] (2013). Evidence for the dipole nature of the low-energy γ enhancement in 56Fe. Physical Review Letters. ISSN 0031-9007. 111(24). doi: 10.1103/PhysRevLett.111.242504. Full text in Research Archive Show summary

  The γ-ray strength function of 56Fe has been measured from proton-γ coincidences for excitation energies up to ≈11  MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the (3He,αγ)56Fe reaction, is confirmed with the (p,p′γ)56Fe experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions. © 2013 American Physical Society

• Guttormsen, Magne Sveen; Jurado, Beatriz; Wilson, J. N.; Aiche, M; Bernstein, L. A. & Ducasse, Quentin [Show all 19 contributors for this article] (2013). Constant-temperature level densities in the quasicontinuum of Th and U isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 88(2). doi: 10.1103/PhysRevC.88.024307. Full text in Research Archive Show summary

  Particle-γ coincidences have been measured to obtain γ-ray spectra as a function of excitation energy for 231–233Th and 237–239U. The level densities, which were extracted using the Oslo method, show a constant temperature behavior. The isotopes display very similar temperatures in the quasicontinuum, however, the even-odd isotopes reveal a constant entropy increase ΔS compared to their even-even neighbors. The entropy excess depends on available orbitals for the last unpaired valence neutron of the heated nuclear system. Also, experimental microcanonical temperature and heat capacity have been extracted. Several poles in the heat capacity curve support the idea that an almost continuous melting of Cooper pairs is responsible for the constant-temperature behavior. © 2013 American Physical Society

• Koehler, Paul Edward; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Siem, Sunniva & Guber, K. H. (2013). Extreme nonstatistical effects in γ decay of 95Mo neutron resonances. Physical Review C. Nuclear Physics. ISSN 0556-2813. 88(4). doi: 10.1103/PhysRevC.88.041305. Full text in Research Archive Show summary

  We demonstrate that high-quality total radiation width (ﰀγ ) data are a virtually untapped resource for testing and improving nuclear models. To this end, we obtained unprecedentedly large sets of ﰀγ values for all six s- and p-wave Jπ values for 95Mo neutron resonances. We show that ﰀγ distributions simulated in the framework of the nuclear statistical model are in sharp disagreement with the data. Simulations modified to include doorway effects resulted in much better agreement. These results call into question the reliability of the nuclear statistical model.

• Larsen, Ann-Cecilie; Bürger, Alexander; Goriely, Stephane; Guttormsen, Magne Sveen; Görgen, Andreas & Eriksen, Tomas Kvalheim [Show all 16 contributors for this article] (2013). Astrophysical reaction rates and the low-energy enhancement in the γ strength. Acta Physica Polonica B. ISSN 0587-4254. 44(3), p. 563–566. doi: 10.5506/APhysPolB.44.563. Full text in Research Archive
• Larsen, Ann-Cecilie; Bürger, Alexander; Goriely, Stephane; Guttormsen, Magne Sveen; Görgen, Andreas & Hagen, Trine Wiborg [Show all 15 contributors for this article] (2013). Transitional γ strength in Cd isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 87(1). doi: 10.1103/PhysRevC.87.014319. Full text in Research Archive Show summary

  The level densities and γ-ray strength functions of 105,106,111,112Cd have been extracted from particle-γ coincidence data using the Oslo method. The level densities are in very good agreement with known levels at low excitation energy. The γ-ray strength functions display no strong enhancement for low γ energies. However, more low-energy strength is apparent for 105,106Cd than for 111,112Cd. For γ energies above ≈4 MeV, there is evidence for some extra strength, similar to what has been previously observed for the Sn isotopes. The origin of this extra strength is unclear; it might be due to E1 and M1 transitions originating from neutron skin oscillations or the spin-flip resonance, respectively. © 2013 American Physical Society

• Voinov, Alexander; Grimes, S.M.; Brune, C.R.; Bürger, Alexander; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 9 contributors for this article] (2013). Experimental differential cross sections, level densities, and spin cutoffs as a testing ground for nuclear reaction codes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 88(5). doi: 10.1103/PhysRevC.88.054607. Full text in Research Archive
• Ducasse, Q; Jurado, B; Aiche, M; Mathieu, L; Tornyi, Tamas Gabor & Görgen, Andreas [Show all 28 contributors for this article] (2013). Neutron-induced cross sections of actinides via the surrogate-reaction method. The European Physical Journal Conferences. ISSN 2101-6275. 42. doi: 10.1051/epjconf/20134201003. Full text in Research Archive
• Guttormsen, Magne Sveen; Bernstein, Lee; Bürger, Alexander; Görgen, Andreas; Gunsing, Frank & Hagen, Trine Wiborg [Show all 11 contributors for this article] (2013). Observation of large orbital scissors strength in actinides. Acta Physica Polonica B. ISSN 0587-4254. 44(3), p. 567–570. doi: 10.5506/APhysPolB.44.567. Full text in Research Archive
• Wilson, J.N.; Gunsing, Frank; Bernstein, Lee; Bürger, Alexander; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 13 contributors for this article] (2012). Level Densities in the actinide region and indirect (n,gamma) cross section measurements using the surrogate method. The European Physical Journal Conferences. ISSN 2101-6275. 21. doi: 10.1051/epjconf/20122101003. Full text in Research Archive
• Wilson, J.N.; Gunsing, F.; Bernstein, L.A.; Bürger, Alexander; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 16 contributors for this article] (2012). Indirect (n, gamma) cross sections of thorium cycle nuclei using the surrogate method. Physical Review C. Nuclear Physics. ISSN 0556-2813. 85(3). doi: 10.1103/PhysRevC.85.034607. Full text in Research Archive
• Larsen, Ann-Cecilie; Goriely, Stephane; Bürger, Alexander; Guttormsen, Magne Sveen; Görgen, Andreas & Harrisopulos, Sotirios [Show all 21 contributors for this article] (2012). Primary gamma-ray spectra in Ti-44 of astrophysical interest. Physical Review C. Nuclear Physics. ISSN 0556-2813. 85(1). doi: 10.1103/PhysRevC.85.014320. Full text in Research Archive
• Bürger, Alexander; Larsen, Ann-Cecilie; Hilaire, Stephane; Guttormsen, Magne Sveen; Harrisopulos, Sotirios & Kmiecik, Maria [Show all 17 contributors for this article] (2012). Nuclear level density and γ-ray strength function of 43Sc. Physical Review C. Nuclear Physics. ISSN 0556-2813. 85(6). doi: 10.1103/PhysRevC.85.064328. Full text in Research Archive
• Guttormsen, Magne Sveen; Bernstein, Lee; Bürger, Alexander; Görgen, Andreas; Gunsing, Frank & Hagen, Trine Wiborg [Show all 11 contributors for this article] (2012). Observation of Large Scissors Resonance Strength in Actinides. Physical Review Letters. ISSN 0031-9007. 109(16). doi: 10.1103/PhysRevLett.109.162503. Full text in Research Archive Show summary

  The orbital M1 scissors resonance has been measured for the first time in the quasicontinuum of actinides. Particle-γ coincidences are recorded with deuteron and 3He-induced reactions on 232Th. The residual nuclei 231,232,233Th and 232,233  Pa show an unexpectedly strong integrated strength of BM1=11–15μ2n in the Eγ=1.0–3.5  MeV region. The increased γ-decay probability in actinides due to scissors resonance is important for cross-section calculations for future fuel cycles of fast nuclear reactors and may also have an impact on stellar nucleosynthesis. © 2012 American Physical Society

• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander; Görgen, Andreas; Nyhus, Hilde-Therese & Siem, Sunniva [Show all 21 contributors for this article] (2012). Do light nuclei display a universal gamma-ray strength function? Europhysics letters. ISSN 0295-5075. 21:04004. doi: 10.1051/epjconf/20122104004. Full text in Research Archive
• Nyhus, Hilde-Therese; Siem, Sunniva; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander & Syed, Naeem Ul Hasan [Show all 9 contributors for this article] (2012). Level density and thermodynamic properties of dysprosium isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 85(1). doi: 10.1103/PhysRevC.85.014323. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander; Görgen, Andreas; Harissopulos, Sotirios & Kmiecik, Maria [Show all 21 contributors for this article] (2011). Fermi’s golden rule applied to the γ decay in the quasicontinuum of 46Ti. Physical Review C. Nuclear Physics. ISSN 0556-2813. 83(014312). doi: 10.1103/PhysRevC.83.014312. Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Brune, C.R.; Bürger, Alexander; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 10 contributors for this article] (2011). Equilibrium and pre-equilibrium processes in the Mn-55(Li-6,xp) and Fe-57(alpha,xp) reactions. Physical Review C. Nuclear Physics. ISSN 0556-2813. 83(5), p. 054605–054605. doi: 10.1103/PhysRevC.83.054605. Full text in Research Archive
• Hagen, Trine Wiborg; Lopez-Martens, A.; Hauschild, K; Belozerov, A. V.; Chelnokov, M. L. & Chepigin, V. I. [Show all 32 contributors for this article] (2011). SPECTROSCOPY OF TRANSFERMIUM NUCLEI USING THE GABRIELA SETUP. Acta Physica Polonica B. ISSN 0587-4254. 42(3-4), p. 605–608. doi: 10.5506/APhysPolB.42.605. Full text in Research Archive
• Larsen, Ann-Cecilie; Goriely, Stephane; Algin, Emel; Agvaanluvsan, Undraa; Bürger, Annetta & Görgen, Andreas [Show all 22 contributors for this article] (2011). Gamma-ray strength functions and their relation to astrophysics. AIP Conference Proceedings. ISSN 0094-243X. 1377, p. 239–246. doi: 10.1063/1.3628386. Full text in Research Archive
• Guttormsen, Magne Sveen; Bürger, Alexander; Hansen, Thor-Erik & Lietaer, Nicolas (2011). The SiRi particle-telescope system. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 648(1), p. 168–173. doi: 10.1016/j.nima.2011.05.055. Full text in Research Archive Show summary

  A silicon particle-telescope system for light-ion nuclear reactions is described. In particular, the system is optimized for level density and γ‐ray strength function measurements with the so-called Oslo method. Eight trapezoidal modules are mounted at 5 cm distance from the target, covering eight forward angles between θ=40∘ and 54°. The thin front ΔE detectors are segmented into eight pads, determining the reaction angle θ for the outgoing charged ejectile. Guard rings on the thick back E detectors guarantee low leakage current at high depletion voltage.

• Lopez-Martens, A; Hagen, Trine Wiborg; Görgen, Andreas; Guttormsen, Magne Sveen; Lønnroth, Tom & Nyhus, Hilde-Therese [Show all 9 contributors for this article] (2011). Spectroscopy of 253No and its daughters. Nuclear Physics A. ISSN 0375-9474. 852, p. 15–15. Full text in Research Archive
• Toft, Heidi Kristine; Larsen, Ann-Cecilie; Bürger, Alexander; Guttormsen, Magne Sveen; Görgen, Andreas & Nyhus, Hilde-Therese [Show all 10 contributors for this article] (2011). Evolution of the pygmy dipole resonance in Sn isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 83(4). doi: 10.1103/PhysRevC.83.044320. Full text in Research Archive
• Lönnroth, Tom; Källman, K-M; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Manngård, P (2011). Study of the high-lying, high-spin alpha+Si-28 resonance structure in S-32. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 38(3). doi: 10.1088/0954-3899/38/3/035107. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Krticka, Milan; Betak, Emil; Bürger, Alexander & Görgen, Andreas [Show all 14 contributors for this article] (2011). Analysis of possible systematic errors in the Oslo method. Physical Review C. Nuclear Physics. ISSN 0556-2813. 83. doi: 10.1103/PhysRevC.83.034315. Full text in Research Archive
• Guttormsen, Magne Sveen; Agvaanluvsan, U; Algin, E; Bürger, Alexander; Larsen, Anja C V & Mitchell, Gary E. [Show all 10 contributors for this article] (2010). Properties of warm nuclei in the quasi-continuum. Europhysics letters. ISSN 0295-5075. 2. doi: 10.1051/epjconf/20100204001. Full text in Research Archive
• Voinov, A; Grimes, SM; Brune, CR; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Massey, TN [Show all 8 contributors for this article] (2010). gamma-strength functions in Ni-60 from two-step cascades following proton capture. Physical Review C. Nuclear Physics. ISSN 0556-2813. 81(2). doi: 10.1103/PhysRevC.81.024319. Full text in Research Archive
• Larsen, Ann-Cecilie; Agvaanluvsan, Undraa; Bernstein, L. A.; Bürger, Alexander; Chankova, Rosita & Goriely, S [Show all 15 contributors for this article] (2010). Soft structures of γ-ray strength functions studied with the Oslo method. Proceedings of Science (PoS). 2(03001). doi: 10.1051/epjconf/20100203001. Full text in Research Archive
• Hauschild, Karl; Lopez-martens, A.; Hagen, Trine Wiborg; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Nyhus, Hilde-Therese [Show all 10 contributors for this article] (2010). Spectroscopy of transfermium nuclei using the GABRIELA set up at the focal plane of the VASSILISSA recoil separator. AIP Conference Proceedings. ISSN 0094-243X. 1224, p. 269–278. doi: 10.1063/1.3431424. Full text in Research Archive
• Toft, Heidi Kristine; Larsen, Ann-Cecilie; Agvaanluvsan, Undraa; Bürger, Alexander; Guttormsen, Magne Sveen & Mitchell, Gary [Show all 11 contributors for this article] (2010). Level densities and gamma-ray strength functions in Sn isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. c81(064311). Full text in Research Archive
• Nyhus, Hilde-Therese; Siem, Sunniva; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander & Syed, Naeem Ul Hasan [Show all 8 contributors for this article] (2010). Radiative strength functions in Dy-163,Dy-164. Physical Review C. Nuclear Physics. ISSN 0556-2813. 81(2). doi: 10.1103/PhysRevC.81.024325. Full text in Research Archive
• Goldblum, B.l.; Prussin, S.g.; Bernstein, Lee; Younes, W.; Guttormsen, Magne Sveen & Nyhus, Hilde-Therese (2010). Surrogate ratio methodology for the indirect determination of neutron capture cross sections. Physical Review C. Nuclear Physics. ISSN 0556-2813. 81(5). doi: 10.1103/PhysRevC.81.054606. Full text in Research Archive
• Bürger, Alexander; Larsen, Anette Cecilie; Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Harissopulos, Sotirios & Kmiecik, M. [Show all 17 contributors for this article] (2010). Level Densities and gamma Strength Functions in Light Sc and Ti Isotopes. Europhysics letters. ISSN 0295-5075. 2. doi: 10.1051/epjconf/20100203003. Full text in Research Archive
• Agvaanluvsan, Undraa; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Mitchell, Gary E. & Schiller, Andreas [Show all 8 contributors for this article] (2009). Evidence for the pair-breaking process in 116,117Sn. Physical Review C. Nuclear Physics. ISSN 0556-2813. 79(1). doi: 10.1103/PhysRevC.79.014320. Full text in Research Archive
• Syed, Naeem Ul Hasan; Larsen, Ann-Cecilie; Bürger, Alexander; Guttormsen, Magne Sveen; Harissopulos, S & Kmiecik, M [Show all 16 contributors for this article] (2009). Extraction of thermal and electromagnetic properties in Ti-45. Physical Review C. Nuclear Physics. ISSN 0556-2813. 80(4). doi: 10.1103/PhysRevC.80.044309. Full text in Research Archive
• Agvaanluvsan, U; Larsen, Ann-Cecilie; Chankova, R; Guttormsen, Magne Sveen; Mitchell, GE & Schiller, A [Show all 8 contributors for this article] (2009). Enhanced Radiative Strength in the Quasicontinuum of Sn-117. Physical Review Letters. ISSN 0031-9007. 102(16). doi: 10.1103/PhysRevLett.102.162504. Full text in Research Archive
• Schiller, Andreas; Agvaanluvsan, Undraa; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Siem, Sunniva (2009). Level density and radiative strength of 116,117Sn. AIP Conference Proceedings. ISSN 0094-243X. Full text in Research Archive
• Siem, Sunniva; Agvaanluvsan, Undraa; Bürger, Alexander; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Nyhus, Hilde-Therese [Show all 11 contributors for this article] (2009). Level densities and radiative strength functions. AIP Conference Proceedings. ISSN 0094-243X. 1090, p. 66–73. doi: 10.1063/1.3087125. Full text in Research Archive
• Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Ingebretsen, Finn; Larsen, Ann-Cecilie; Lonnroth, T & Rekstad, John Bernhard [Show all 9 contributors for this article] (2009). Level density and gamma-decay properties of closed shell Pb nuclei. Physical Review C. Nuclear Physics. ISSN 0556-2813. 79(2). doi: 10.1103/PhysRevC.79.024316. Full text in Research Archive
• Nyhus, Hilde-Therese; Siem, Sunniva; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander & Syed, Naeem Ul Hasan [Show all 9 contributors for this article] (2009). Level Densities, Thermodynamics and Gamma-ray Strength Functions in 163,164Dy. Acta Physica Polonica B. ISSN 0587-4254. 40(3), p. 593–596. Full text in Research Archive
• Voinov, AV; Oginni, BM; Grimes, SM; Brune, CR; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 9 contributors for this article] (2009). Nuclear excitations at constant temperature. Physical Review C. Nuclear Physics. ISSN 0556-2813. 79(3). doi: 10.1103/PhysRevC.79.031301. Full text in Research Archive
• Hauschild, K; Lopez-Martens, A; Yeremin, AV; Dorvaux, O; Antalic, S & Belozerov, AV [Show all 31 contributors for this article] (2008). High-K, t(1/2)=1.4(1) ms, isomeric state in Lr-255. Physical Review C. Nuclear Physics. ISSN 0556-2813. 78. doi: 10.1103/PhysRevC.78.021302. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne Sveen; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard & Syed, Naeem Ul Hasan [Show all 12 contributors for this article] (2008). Experimental Level densities and gamma-strength functions in rare earth nuclei. AIP Conference Proceedings. ISSN 0094-243X. 1005. Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Larsen, Ann-Cecilie; Brune, C.R.; Guttormsen, Magne Sveen & Massey, T.N. [Show all 9 contributors for this article] (2008). Level densities of 44Sc and 47Ti from different experimental techniques. Physical Review C. Nuclear Physics. ISSN 0556-2813. 77(034613). doi: 10.1103/PhysRevC.77.034613. Full text in Research Archive
• Guttormsen, Magne Sveen & Olsen, Dag Rune (2008). Kreftterapi med lette ioner. HMT - Helsetjenesten Medisinsk Teknikk : helse, medisin, teknikk. ISSN 1501-7729. p. 7–8. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva & Syed, Naeem Ul Hasan [Show all 7 contributors for this article] (2008). Thermodynamic properties of atomic nuclei with T<1 MeV. AIP Conference Proceedings. ISSN 0094-243X. 1012, p. 198–202. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom & Rekstad, John Bernhard [Show all 11 contributors for this article] (2008). Experimental nuclear level densities and gamma-ray strength functions in Sc and V isotopes. AIP Conference Proceedings. ISSN 0094-243X. 1005, p. 70–73. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom & Rekstad, John Bernhard [Show all 11 contributors for this article] (2008). Puzzling gamma-ray strength functions in 44,45Sc and 50,51V. AIP Conference Proceedings. ISSN 0094-243X. p. 380–382. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne Sveen; Chankova, Rositsa; Larsen, Ann-Cecilie; Nyhus, Hilde-Therese & Rekstad, John Bernhard [Show all 10 contributors for this article] (2008). Level densities and gamma-strength functions in Sm isotopes. AIP Conference Proceedings. ISSN 0094-243X. p. 425–427. Full text in Research Archive
• Dorvaux, Olivier; Lopez-Martens, Araceli; Hauschild, Karl; Yeremin, A. V.; Khouaja, A. & Belozerov, A. V. [Show all 33 contributors for this article] (2008). Spectroscopy of heavy elements at Dubna. AIP Conference Proceedings. ISSN 0094-243X. 1012, p. 64–68. Full text in Research Archive
• Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Ingebretsen, Finn; Larsen, Ann-Cecilie; Siem, Sunniva & Lönnroth, Tom [Show all 8 contributors for this article] (2008). The Oslo Method and Its Application to Lead Isotopes. AIP Conference Proceedings. ISSN 0094-243X. p. 428–430. Full text in Research Archive
• Hauschild, Karl; Lopez-Martens, Araceli; Yeremin, A. V.; Dorvaux, Olivier; Belozerov, A. V. & Chelnokov, M. L. [Show all 26 contributors for this article] (2008). Half-life and excitation energy of the I^{\pi}=13/2+ isomer in 209Ra. Physical Review C. Nuclear Physics. ISSN 0556-2813. 77. doi: 10.1103/PhysRevC.77.047305. Full text in Research Archive
• Goldblum, B.l.; Prussin, S.g.; Agvaanluvsan, Undraa; Bernstein, Lee; Bleuel, D.l. & Younes, W. [Show all 7 contributors for this article] (2008). Determination of (n,γ) cross sections in the rare-earth region using the surrogate ratio method. Physical Review C. Nuclear Physics. ISSN 0556-2813. C78(064606). Full text in Research Archive
• Algin, Emel; Agvaanluvsan, Undraa; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Mitchell, Gary & Rekstad, John Bernhard [Show all 9 contributors for this article] (2008). Thermodynamic properties of 56,57Fe. Physical Review C. Nuclear Physics. ISSN 0556-2813. C78(054321). Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Brune, C.R.; Guttormsen, Magne Sveen; Massey, T.N. & Schiller, Andreas [Show all 7 contributors for this article] (2008). Experimental Study of Level Density and gamma-strength Functions from Compound Nuclear Reactions. AIP Conference Proceedings. ISSN 0094-243X. 1005, p. 61–64. Full text in Research Archive
• Lopez-Martens, Araceli; Hauschild, Karl; Yeremin, Alexander; Dorvaux, Olivier; Belozerov, A. V. & Briancon, Ch. [Show all 32 contributors for this article] (2007). Isomeric states in No-253. European Physical Journal A. ISSN 1434-6001. 32(3), p. 245–250. doi: 10.1140/epja/i2007-10391-8. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom & Messelt, Svein [Show all 11 contributors for this article] (2007). Nuclear level densities and gamma-ray strength functions in Sc-44,Sc-45. Physical Review C. Nuclear Physics. ISSN 0556-2813. doi: 10.1103/PhysRevC.76.044303. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Chankova, Rosita; Larsen, Ann-Cecilie; Rekstad, John Bernhard & Schiller, Andreas [Show all 7 contributors for this article] (2007). Level densities and gamma strength functions in Sm-146,Sm-147 nuclei. Acta Physica Polonica B. ISSN 0587-4254. 38(4), p. 1499–1502. Full text in Research Archive
• Yeremin, A.V.; Belozerov, A. V.; Chelnokov, M.L.; Chepigin, V. I.; Gorshkov, V.A. & Guttormsen, Magne Sveen [Show all 30 contributors for this article] (2007). Gamma and electron spectroscopy of heavy nuclei at FLNR JINR. AIP Conference Proceedings. ISSN 0094-243X. 912, p. 119–126. Full text in Research Archive Show summary

  Detailed spectroscopic information of excited nuclear states in deformed transfermium nuclei is scarce. Most of the information available today has been obtained from investigations of fine structure decay. Although decay gives access to hindrance factors and lifetimes which are strongly correlated to shell/subshell closures and the presence of isomers, only the combined use of and conversion electron spectroscopy allows the precise determination of excitation energy, spin and parity of nuclear levels. In particular, the study of odd isotopes gives crucial information on the single particle states available at and around the Fermi surface. In the following, the preliminary results of decay studies using - and - beta coincidences at the focal plane of the VASSILISSA recoil separator are presented

• Algin, E; Schiller, A; Voinov, A; Agvaanluvsan, U; Belgya, T & Bernstein, LA [Show all 19 contributors for this article] (2007). Bulk properties of iron isotopes. Physics of Atomic Nuclei. ISSN 1063-7788. 70, p. 1634–1639. doi: 10.1134/S1063778807090232. Full text in Research Archive
• Guttormsen, Magne; Chankova, Rosita; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Siem, Sunniva & Syed, Naeem Ul Hasan [Show all 9 contributors for this article] (2007). The role of broken cooper pairs in warm nuclei. Acta Physica Polonica B. ISSN 0587-4254. 38(4), p. 1489–1493. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne; Chankova, Rosita; Ingebretsen, Finn; Lönnroth, Tom & Messelt, Svein [Show all 12 contributors for this article] (2007). Radiative strength functions of warm nuclei in the 1f(7/2) shell. Acta Physica Polonica B. ISSN 0587-4254. 38(4), p. 1495–1498. Full text in Research Archive
• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Hjorth-Jensen, Morten; Rekstad, John Bernhard & Schiller, Andreas [Show all 10 contributors for this article] (2006). Single particle entropy in heated nuclei. AIP Conference Proceedings. ISSN 0094-243X. 831, p. 162–166. Full text in Research Archive
• Chankova, Rositsa; Guttormsen, Magne; Schiller, Andreas; Larsen, Ann-Cecilie; Voinov, Alexander & Siem, Sunniva [Show all 8 contributors for this article] (2006). Nuclear properties in the vicinity of closed shells. AIP Conference Proceedings. ISSN 0094-243X. 831, p. 421–423. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne; Chankova, Rositsa; Ingebretsen, Finn; Lønnroth, Tom & Messelt, Svein [Show all 12 contributors for this article] (2006). Heating nuclei in the mass region of A = 40-50. AIP Conference Proceedings. ISSN 0094-243X. 831, p. 544–547. Full text in Research Archive
• Syed, Naeem Ul Hasan; Guttormsen, Magne; Siem, Sunniva; Ingebretsen, Finn; Lønnroth, Tom & Rekstad, John Bernhard [Show all 10 contributors for this article] (2006). Extracting experimental level densities in A=207-208 Nuclei. AIP Conference Proceedings. ISSN 0094-243X. 831, p. 548–550. Full text in Research Archive
• Larsen, Ann-Cecilie; Chankova, Rositsa; Guttormsen, Magne; Ingebretsen, Finn; Messelt, Svein & Rekstad, John Bernhard [Show all 12 contributors for this article] (2006). Microcanonical entropies and radiative strength functions of 50,51V. Physical Review C. Nuclear Physics. ISSN 0556-2813. 73. doi: 10.1103/PhysRevC.73.064301. Full text in Research Archive
• Chankova, Rositsa; Schiller, A; Agvaanluvsan, U; Algin, E; Bernstein, LA & Guttormsen, Magne [Show all 15 contributors for this article] (2006). Level densities and thermodynamical quantities of heated Mo93-98 isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 73. Full text in Research Archive
• Lopez-Martens, A.; Hauschild, Karl; Yeremin, A.V.; Belozerov, A.V.; Briancon, C. & Chelnokov, M.L. [Show all 30 contributors for this article] (2006). Detailed spectroscopy of Fm-249. Physical Review C. Nuclear Physics. ISSN 0556-2813. 74. Full text in Research Archive
• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard & Schiller, Andreas [Show all 9 contributors for this article] (2006). Experimental nuclear level densities and interpretation within the microcanonical ensemble. Proceedings of Science (PoS). Full text in Research Archive Show summary

  Statistical properties of atomic nuclei are studied as function of the number of neutrons. The experimental method is based on particle-g coincidences measured in light-ion reactions with one charged ejectile. From particle-g coincidences, level densities and radiative strength functions can be simultaneously extracted from one and the same data set. Mid-shell nuclei show significant odd-even entropy differences interpreted as the single-particle entropy of the valence nucleon. However, these properties change when approaching closed shells. A model within the framework of the microcanonical ensemble is presented and compared with data from the molybdenum isotopes. The odd-even entropy difference disappears in the vicinity of the N =50 shell, and an overshoot of positive parity states is predicted.

• Schiller, A; Voinov, AV; Algin, E; Bernstein, LA; Garrett, PE & Guttormsen, Magne [Show all 9 contributors for this article] (2006). Primary versus secondary gamma intensities in Yb-171(n(th), gamma). Physical Review C. Nuclear Physics. ISSN 0556-2813. 74. Full text in Research Archive
• Algin, Emel; Schiller, Andreas; Guttormsen, Magne Sveen; Hjorth-Jensen, Morten; Rekstad, John Bernhard & Siem, Sunniva [Show all 7 contributors for this article] (2006). Bulk Properties of Iron Isotopes. Physics of Atomic Nuclei. ISSN 1063-7788. 70(9), p. 1634–1639. Full text in Research Archive
• Kaneko, K.; Hasegawa, M.; Agvaanluvsan, Undraa; Algin, Emel; Chankova, Rositsa & Guttormsen, Magne [Show all 12 contributors for this article] (2006). Breaking of nucleon Cooper pairs at finite temperature in 93-98Mo. Physical Review C. Nuclear Physics. ISSN 0556-2813. 74. Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Agvaanluvsan, Undraa; Algin, Emel; Belgya, Thomas & Brune, C.R. [Show all 13 contributors for this article] (2006). Level densities of iron isotopes and low-energy enhancement of gamma-strength function. AIP Conference Proceedings. ISSN 0094-243X. 819, p. 545–549. Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Agvaanluvsan, Undraa; Algin, Emel; Belgya, Thomas & Brune, C.R. [Show all 13 contributors for this article] (2006). Level density of 56Fe and low-energy enhancement of gamma-strength function. Physical Review C. Nuclear Physics. ISSN 0556-2813. 74. Full text in Research Archive
• Schiller, Andreas; Voinov, Alexander; Algin, Emel; Becker, J.A.; Bernstein, Lee & Garrett, P.E. [Show all 10 contributors for this article] (2006). Low-energy M1 excitation mode in 172Yb. Physics Letters B. ISSN 0370-2693. B633, p. 225–230. Full text in Research Archive
• Guttormsen, Magne; Chankova, Rositsa; Agvaanluvsan, U; Algin, E; Bernstein, LA & Ingebretsen, Finn [Show all 15 contributors for this article] (2005). Radiative strength functions in Mo93-98. Physical Review C. Nuclear Physics. ISSN 0556-2813. 71. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Algin, E; Agvaanluvsan, U; Belgya, T & Chankova, Rositsa [Show all 13 contributors for this article] (2005). Soft resonances in hot nuclei. Acta Physica Polonica B. ISSN 0587-4254. 36. Full text in Research Archive
• Sunde, Ann-Cecilie; Guttormsen, Magne; Chankova, Rositsa; Ingebretsen, Finn; Lonnroth, T & Messelt, Svein [Show all 12 contributors for this article] (2005). Thermal and electromagnetic properties of the light vanadium isotopes. Acta Physica Polonica B. ISSN 0587-4254. 36. Full text in Research Archive
• Agvaanluvsan, U; Algin, E; Becker, JA; Guttormsen, Magne; Mitchell, GE & Siem, Sunniva [Show all 8 contributors for this article] (2005). Investigation of the radiative strength function. Nuclear Instruments and Methods in Physics Reseach B. ISSN 0168-583X. 241. Full text in Research Archive
• Schiller, Andreas; Agvaanluvsan, Undraa; Algin, Emel; Bagheri, Asadolla; Chankova, Rosita & Guttormsen, Magne [Show all 11 contributors for this article] (2005). Nuclear thermodynamics below particle threshold. AIP Conference Proceedings. ISSN 0094-243X. p. 216–228. Full text in Research Archive
• Siem, Sunniva; Agvaanluvsan, Undraa; Algin, Emel; Belgya, Thomas; Bernstein, Lee & Chankova, Rosita [Show all 17 contributors for this article] (2005). Entropy in hot nuclei. AIP Conference Proceedings. ISSN 0094-243X. 764, p. 315–320. Full text in Research Archive
• Voinov, Alexander; Algin, Emel; Agvaanluvsan, Undraa; Belgya, Thomas; Chankova, Rosita & Guttormsen, Magne [Show all 10 contributors for this article] (2004). Large enhancement of radiative strength for soft transitions in the quasicontinuum. Physical Review Letters. ISSN 0031-9007. 93(14). doi: 10.1103/PhysRevLett.93.142504. Full text in Research Archive
• Agvaanluvsan, Undraa; Schiller, Andreas; Becker, J.A.; Bernstein, Lee; Garrett, P.E. & Guttormsen, Magne [Show all 11 contributors for this article] (2004). Level densities and gamma-ray strength functions in 170,171,172Yb. Physical Review C. Nuclear Physics. ISSN 0556-2813. 70. doi: 10.1103/PhysRevC.70.054611. Full text in Research Archive
• Voinov, Alexander; Schiller, Andreas; Algin, Emel; Bernstein, Lee; Garrett, P.E. & Guttormsen, Magne [Show all 9 contributors for this article] (2004). Nature of pygmy resonance in continuous gamma-spectra. Physics of Atomic Nuclei. ISSN 1063-7788. 67. Full text in Research Archive
• Guttormsen, Magne; Bagheri, Asadolla; Chankova, Rosita; Rekstad, John Bernhard; Siem, Sunniva & Schiller, A [Show all 7 contributors for this article] (2003). Thermal properties and radiative strengths in Dy-160,Dy-161,Dy-162. Physical Review C. Nuclear Physics. ISSN 0556-2813. 68, p. art. no.–064306. Full text in Research Archive
• Voinov, Alexander; Schiller, Andreas; Guttormsen, Magne; Rekstad, John Bernhard & Siem, Sunniva (2003). DETERMINATION OF THE ELECTROMAGNETIC CHARACTER OF SOFT DIPOLE MODES SOLELY BASED ON QUASICONTINUOUS GAMMA SPECTROSCOPY. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 497, p. 350–358. Full text in Research Archive
• Guttormsen, Magne Sveen; Melby, Elin; Rekstad, John Bernhard; Siem, Sunniva; Schiller, Andreas & al.,, - et (2003). Level density and γ-ray strength in 27,28Si. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 29, p. 263–263. Full text in Research Archive
• Tavukcu, Emel; Becker, J.A.; Bernstein, Lee; Garrett, P.E.; Guttormsen, Magne & Mitchell, Gary [Show all 11 contributors for this article] (2003). Thermodynamical properties of 56Fe. AIP Conference Proceedings. ISSN 0094-243X. 656(1). Full text in Research Archive
• Tavukcu, Emel; Becker, J.A.; Bernstein, Lee; Garrett, P.E.; Guttormsen, Magne & Mitchell, Gary [Show all 11 contributors for this article] (2003). Average nuclear level densities and radiative strength functions in 56,57Fe from primary gamma-spectra. AIP Conference Proceedings. ISSN 0094-243X. 680, p. 296–299. Full text in Research Archive
• Schiller, A; Algin, Emel; Bernstein, Lee; Garrett, P.E.; Guttormsen, Magne & Hjorth-Jensen, Morten [Show all 12 contributors for this article] (2003). Level densities in Fe-56,Fe-57 and Mo-96,Mo-97. Physical Review C. Nuclear Physics. ISSN 0556-2813. 68, p. art. no.–054326. Full text in Research Archive
• Guttormsen, Magne; Bagheri, Assadollah; Chankova, Rositsa; Rekstad, John Bernhard; Siem, Sunniva & Schiller, Andreas [Show all 7 contributors for this article] (2003). THERMAL PROPERTIES AND RADIATIVE STRENGTHS IN DY-160,161,162. Physical Review C. Nuclear Physics. ISSN 0556-2813. 68(064306). Full text in Research Archive
• Guttormsen, Magne; Chankova, Rositsa; Hjorth-Jensen, Morten; Rekstad, John Bernhard; Siem, Sunniva & Schiller, Andreas [Show all 7 contributors for this article] (2003). FREE ENERGY AND CRITICALITY IN THE NUCLEON PAIR BREAKING PROCESS. Physical Review C. Nuclear Physics. ISSN 0556-2813. 68(034311). Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Ingeberg, Kristian; Melby, Elin; Rekstad, John Bernhard & Schiller, Andreas [Show all 7 contributors for this article] (2002). Level densities and gamma strength functions in 148,149Sm. Physical Review C. Nuclear Physics. ISSN 0556-2813. 65(044318). Full text in Research Archive
• Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard; Siem, Sunniva; Schiller, Andreas & Lønnroth, Tom [Show all 7 contributors for this article] (2002). Level density and gamma-ray strength in 27,28Si. http://xxx.lanl.gov/abs/nucl-ex/0203013 and J. Phys. G: Nucl. Part. Phys. 29, 263 (2003). Full text in Research Archive Show summary

  A method to extract simultaneously level densities and gamma-ray transmission coefficients has for the first time been tested on light nuclei utilizing the 28Si(3He,alpha gamma)27Si and 28Si(3He,3He' gamma)28Si reactions. The extracted level densities for 27Si and 28Si are consistent with the level densities obtained by counting known levels in the respective nuclei. The extracted gamma-ray strength in 28Si agrees well with the known gamma-decay properties of this nucleus. Typical nuclear temperatures are found to be T appr. 2.4 MeV at around 7 MeV excitation energy. The entropy gap between nuclei with mass number A and A + - 1 is measured to be delta S appr. 1.0 k_B, which indicates an energy spacing between single-particle orbitals comparable with typical nuclear temperatures.

• Voinov, Alexander; Schiller, Andreas; Guttormsen, Magne; Rekstad, John Bernhard & Siem, Sunniva (2002). Determination of the electromagnetic character of soft dipole modes solely based on quasicontinuous gamma spectroscopy. Los Alamos preprint server. Full text in Research Archive Show summary

  We show that the combined analysis of the quasicontinuous gamma spectra from the (He-3,alpha) and the (n-thermal,2gamma) reactions gives the possibility to measure the electromagnetic character of soft dipole resonances. Two-step gamma-cascade spectra have been calculated, using level densities and radiative strength functions from the (He-3,alpha gamma) reaction. The calculations show that the intensity of the two-step cascades depends on the electromagnetic character of the soft dipole resonance under study. The difference reaches 40-100% which can be measured experimentally.

• Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Rekstad, John Bernhard & Siem, Sunniva (2002). Model for pairing phase transition in atomic nuclei. Physical Review C. Nuclear Physics. ISSN 0556-2813. Full text in Research Archive Show summary

  A model is developed which allows the investigation and classification of the pairing phase transition in atomic nuclei. The regions of the parameter space are discussed for which a pairing phase transition can be observed. The model parameters include: number of particles, attenuation of pairing correlations with increasing seniority, single particle level spacing, and pairing gap parameter. It is argued that for nuclear models, the pairing phase transition has to be separated in temperature from the signal of the exhaustion of the finite model space.

• Ryzhikov, Vladimir D.; Starzhinskiy, Nikolai G.; Gal'chinetskii, Leonid P.; Guttormsen, Magne; Kist, Alexander A. & Klamra, Wlodzimierz (2001). Behaviour of New ZnSe(Te, O) Semiconductor Scintillators under High Doses of Ionizing Radiation. IEEE Transactions on Nuclear Science. ISSN 0018-9499. 48(4), p. 1561–1564. Full text in Research Archive Show summary

  Changes in scintillation and optical properties of scintillators based on ZnSe(Te, O) crystals were studied under influence of ionozing radiations. Accounting for their high light output and low afterglow level, semiconductor scintillators (SCS) is now the most suitable choice of scintillator material for modern X-ray introscopic systems and tomographs, as well as dosimeters for detection of beta- and gamma-radiation at high dose rates.

• Schiller, Andreas; Bjerve, Amund; Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn & Melby, Elin [Show all 9 contributors for this article] (2001). The critical temperature for quenching of pair correlations. Physical Review C. Nuclear Physics. ISSN 0556-2813. 63(021306). Full text in Research Archive
• Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva (2001). Level density and thermal properties in rare earth nuclei. Physics Atomic Nuclei. 64(7), p. 1186–1193. Full text in Research Archive Show summary

  A convergent method to extract the nuclear level density and the -ray strength function from primary -ray spectra has been established. Thermodynamical quantities have been obtained within the microcanonical and canonical ensemble theory. Structures in the caloric curve and in the heat capacity curve are interpreted as fingerprints of breaking of Cooper pairs and quenching of pairing correlations. The strength function can be described using models and common parametrizations for the E1, M1, and pygmy resonance strength. However, a significant decrease of the pygmy resonance strength at finite temperatures has been observed

• Melby, Elin; Guttormsen, Magne; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva & Voinov, Alexander (2001). Thermal and electromagnetic properties of 166Er and 167Er. Physical Review C. Nuclear Physics. ISSN 0556-2813. Full text in Research Archive Show summary

  The primary gamma-ray spectra of 166-Er and 167-Er are deduced from the (3-He,alpha gamma) and (3-He,3-He' gamma) reaction, respectively, enabling a simultaneous extraction of the level density and the gamma-ray strength function. Entropy, temperature and heat capacity are deduced from the level density within the micro-canonical and the canonical ensemble, displaying signals of a phase-like transition from the pair-correlated ground state to an uncorrelated state at Tc=0.5 MeV. The gamma-ray strength function displays a bump around E-gamma=3 MeV, interpreted as the pygmy resonance.

• Voinov, Alexander; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2001). gamma-ray strength function and pygmy resonance in rare earth nuclei. Physical Review C. Nuclear Physics. ISSN 0556-2813. 63(4). Full text in Research Archive
• Ibragimova, E.M.; Oksengendler, B.L.; Masharipov, K.Yu.; Mukhamedshina, N.A.; Gafarov, A.A. & Mkrtchyan, G.A. [Show all 13 contributors for this article] (2001). GAMMA-LUMINESCENCE AND RADIOLYSIS OF ZnSe(Te,O) SCINTILLATORS AFTER HIGH DOSE GAMMA-IRRADIATION. Terrorism and Political Violence. ISSN 0954-6553. 3, p. 75–83. Full text in Research Archive Show summary

  The paper presents the results of studying the product of radiolysis and gamma-luminescence (GL) depending on temperature and dose of gamma-irradiation in new scintillating ZnSe crystals containing Te impurity from 0.01 to 0.6 mass% and subjected to thermal treatment in oxygen flow. The X-ray analysis showed a super-stoichiometric content of zinc in the crystals, consequently, the number of intrinsic defects was estimated ~1020 cm-3 before the irradiation. Spectra of GL at 300 K contain only a wide band at 630-680 nm. Spectra of GL at 77 K are much more intensive than those at 300 K and contain additional bands at 470 and 550 nm. After continuous gamma-irradiation at 300 K to the high dose of 109 R the intensity of GL decreases significantly, besides about 10 nm of subsurface layer damages because of radiolysis. The radiolysis mechanism is considered theoretically in which shock waves generated under ionization produce much damage near the surface.

• Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2001). Heat capacity and pairing transition in nuclei. nucl-ex/0104029 and Phys.Rev. C64, 034319 (2001). 64(Phys. Rev. C), p. 034319–1-034319-7. Full text in Research Archive Show summary

  A simple model based on the canonical-ensemble theory is outlined for hot nuclei. The properties of the model are discussed with respect to the Fermi gas model and the breaking of Cooper pairs. The model describes well the experimental level density of deformed nuclei in various mass regions. The origin of the so-called S-shape of the heat capacity curve Cv(T) is discussed.

• Guttormsen, Magne; Bjerve, Amund; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard & Schiller, Andreas [Show all 8 contributors for this article] (2000). Entropy in hot ^161,162Dy and ^171,172Yb nuclei. Physical Review C. Nuclear Physics. ISSN 0556-2813. C62(024306). Full text in Research Archive
• Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2000). Energy shifted level density in the rare earth region. Physical Review C. Nuclear Physics. ISSN 0556-2813. 61(067302). Full text in Research Archive
• Rekstad, John Bernhard; Bergholt, Lisbeth; Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn & Melby, Elin [Show all 10 contributors for this article] (2000). Measurement of level densities and gamma ray strength functions. AIP Conference Proceedings. ISSN 0094-243X. 529(1), p. 144–151. Full text in Research Archive Show summary

  A method has been developed where primary -rays after nuclear reactions with one ejectile only, can be projected out from the total -ray spectrum. These primary -ray spectra are shown to be, under certain conditions, a new source for determination of nuclear level densities and -ray strength functions. Results for 162Dy, 166Er and 172Yb are presented. The level density is used for determination of nuclear temperature and heat capacity. Fine structures in the level density and the temperature suggest changes in the pair correlation

• Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2000). Entropy of thermally excited particles in nuclei. Physical Review C. Nuclear Physics. ISSN 0556-2813. C63. Full text in Research Archive Show summary

  Information on level density for nuclei with mass numbers A = 20 - 250 is deduced from discrete low-lying levels and neutron resonance data. The odd-mass nuclei exhibit in general 4 - 7 times the level density found for its neighboring even-even nuclei at the same excitation energy. This excess corresponds to an entropy of approx. 1.7 k for the odd particle. The value is approximately constant for all mid-shell nuclei and for all ground state spins. For these nuclei it is argued that the entropy scales with the number of quasiparticles. A simple model based on the canonical ensemble theory accounts qualitatively for the observed properties.

• Martensson, J; Guttormsen, Magne & Løvhøiden, Gunnar (2000). Pion Production Excitation Functions in Proton-Nucleus Collisions from the Absolute Threshold to 500 MeV. Physical Review C. Nuclear Physics. ISSN 0556-2813. C62(014610). Full text in Research Archive
• Schiller, Andreas; Bergholt, Lisbeth; Guttormsen, Magne Sveen; Melby, Elin; Messelt, Svein & Rekstad, John Bernhard [Show all 7 contributors for this article] (2000). Level Densities and g-Strength Functions in Rare Earth Nuclei. Physica Scripta. ISSN 0031-8949. 88, p. 144–144. doi: 10.1238/Physica.Topical.088a00144. Full text in Research Archive
• Voinov, Alexander; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2000). Gamma-ray strength function and pygmy resonance in rare earth nuclei. Los Alamos preprint server. p. 1–11. Full text in Research Archive
• Schiller, Andreas; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard; Siem, Sunniva & Voinov, Alexander (2000). Observation of the scissors mode in the quasicontinuum. Los Alamos preprint server. p. 1–12. Full text in Research Archive
• Melby, Elin; Bergholt, Lisbeth; Guttormsen, Magne Sveen; Hjorth-Jensen, Morten; Ingebretsen, Finn & Messelt, Svein [Show all 10 contributors for this article] (2000). Experimental temperature and heat capacity in rare earth nuclei. Physica Scripta. ISSN 0031-8949. 88, p. 138–138. doi: 10.1238/Physica.Topical.088a00138. Full text in Research Archive
• Schiller, Andreas; Bergholt, Lisbeth; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva (2000). Extraction of level density and gamma strength function from primary gamma spectra. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. A447. Full text in Research Archive Show summary

  We present a new iterative procedure to extract the level density and the gamma strength function from primary gamma spectra for energies close up to the neutron binding energy. The procedure is tested on simulated spectra and on data from the Yb-173(He-3,alpha)Yb-172 reaction.

• Schiller, Andreas; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva (2000). Level density and gamma strength function in 162-Dy from inelastic 3He scattering. Physical Review C. Nuclear Physics. ISSN 0556-2813. Full text in Research Archive Show summary

  Complementary measurements have been performed for the level density and gamma strength function in 162-Dy using inelastic 3-He scattering. Comparing these results to previous measurements using the 163-Dy(3-He,alpha) reaction, reveals that the measured quantities above 1.5 MeV do not depend significantly on the nuclear reaction chosen.

• Greenless, P.T.; Guttormsen, Magne; Messelt, Svein; Schiller, Andreas; Siem, Sunniva & Tveter, Trine Spedstad (1999). Fine structure in the alpha decay of 226U and 230Pu. European Physical Journal A. ISSN 1434-6001. 6(269), p. 289–289. Full text in Research Archive
• Fokin, A.; Guttormsen, Magne & Løvhøiden, Gunnar (1999). d/p and t/p ratios in nucleon-nucleus and heavy ion reactions: Can entropy be determined? Physical Review C. Nuclear Physics. ISSN 0556-2813. 60, p. 0246011–0246017. Full text in Research Archive
• Melby, Elin; Bergholt, Lisbeth; Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn & Messelt, Svein [Show all 10 contributors for this article] (1999). Observation of thermodynamical properties in the <SUP>162</SUP>Dy, <SUP>166</SUP>Er, <SUP>172</SUP>Yb nuclei. Physical Review Letters. ISSN 0031-9007. 83, p. 3150–3153. Full text in Research Archive
• Greenless, P.T.; Kuusiniemi, P.; Amzal, N.; Andreyev, A.; Butler, P.A. & Cann, K.J. [Show all 33 contributors for this article] (1999). Fine structure in the alpha decays of $^{226}U$ and $^{230}Pu$. European Physical Journal A. ISSN 1434-6001. 6(3), p. 269–273. Full text in Research Archive
• Guttormsen, Magne (1999). Testing the statistical nuclear model at the Oslo cyclotron. Nuclear Physics News International. 9(4), p. 33–36. Full text in Research Archive
• Greenless, P.T.; Guttormsen, Magne; Messelt, Svein; Schiller, Andreas; Siem, Sunniva & Tveter, Trine Spedstad (1998). First observation of excited states in <SUP>226</SUP>U. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 24, p. L63–L70. Full text in Research Archive
• Evensen, Lars; Guttormsen, Magne Sveen & et, al. (1997). Thin detectors for the CHICSi Delta(E)-E telescope. IEEE Transactions on Nuclear Science. ISSN 0018-9499. 44, p. 629–634. doi: 10.1109/23.603723. Full text in Research Archive
• Jakobsson, Bo; Guttormsen, Magne Sveen & et, al. (1997). Gross and fine structure of pion production excitation functions in p nucleus and nucleus nucleus reactions. Physical Review Letters. ISSN 0031-9007. 78, p. 3828–3831. doi: 10.1103/PhysRevLett.78.3828. Full text in Research Archive
• Huseby, Ingvild; Tveter, Trine Spedstad; Bergholt, Lisbeth; Guttormsen, Magne Sveen; Melby, Elin & Rekstad, John Bernhard [Show all 8 contributors for this article] (1997). K hindrance in primary gamma decay after thermal and average resonance neutron capture. Physical Review C. Nuclear Physics. ISSN 0556-2813. p. 1805–1809. doi: 10.1103/PhysRevC.55.1805. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1997). CHICSi — a 3π multi-detector system for studying heavy ion interactions inside a storage ring. Nuclear Physics A. ISSN 0375-9474. 626, p. 439–439. Full text in Research Archive
• Tveter, Trine Spedstad; Bergholt, Lisbeth; Guttormsen, Magne Sveen; Melby, Elin & Rekstad, John Bernhard (1996). Observation of Fine Structure in Nuclear Level Densities and gamma-Ray Strength Functions. Physical Review Letters. ISSN 0031-9007. 77, p. 2404–2407. doi: 10.1103/PhysRevLett.77.2404. Full text in Research Archive
• Berg, M.; Guttormsen, Magne Sveen & et, al. (1996). A compact range telescope for K+ measurements. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 381, p. 267–274. doi: 10.1016/S0168-9002(96)00722-X. Full text in Research Archive
• Elmer, R.; Guttormsen, Magne Sveen & et., al. (1996). K+ emission in symmetric heavy ion reactions at subthreshold energies. Physical Review Letters. ISSN 0031-9007. 77, p. 4884–4886. doi: 10.1103/PhysRevLett.77.4884. Full text in Research Archive
• Sheline, R.K.; Bergholt, Lisbeth; Guttormsen, Magne Sveen; Rekstad, John Bernhard & Tveter, Trine Spedstad (1996). DeltaK forbiddenness in neutron capture resonances in Lu-177. Physical Review C. Nuclear Physics. ISSN 0556-2813. 51, p. 3078–3083. doi: 10.1103/PhysRevC.51.3078. Full text in Research Archive
• Guttormsen, Magne Sveen & Chic, Collaboration (1996). A compact range telescope for K+ measurements. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 381(2-3), p. 267–274. Full text in Research Archive
• Guttormsen, Magne Sveen; Tveter, Trine Spedstad; Bergholt, Lisbeth; Ingebretsen, Finn & Rekstad, John Bernhard (1996). The unfolding of continuum gamma-ray spectra. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 374(3), p. 371–376. Full text in Research Archive
• Murin, Yu.; Guttormsen, Magne Sveen & et, al. (1995). Isobaric ratios of fragments emitted in incomplete fusion reactions. Physical Review C. Nuclear Physics. ISSN 0556-2813. 51. doi: 10.1103/PhysRevC.51.2794. Full text in Research Archive
• Jerrestam, D; Guttormsen, Magne Sveen; Rekstad, John Bernhard; Tveter, Trine Spedstad & al.,, - et (1995). In-beam spectroscopic studies of the nucleus 105Cd. Nuclear Physics A. ISSN 0375-9474. 593, p. 162–162. Full text in Research Archive
• Tveter, Trine Spedstad; Guttormsen, Magne Sveen; Rekstad, John Bernhard & al.,, - et (1995). Statistical γ-ray multiplicity distributions in Dy and Yb nuclei. Nuclear Physics A. ISSN 0375-9474. 581, p. 220–220. Full text in Research Archive
• Henden, Lisa; Bergholt, Lisbeth; Guttormsen, Magne Sveen; Rekstad, John Bernhard & Tveter, Trine Spedstad (1995). On the relation between the statistical γ-decay and the level density in 162Dy. Nuclear Physics A. ISSN 0375-9474. 589, p. 249–249. Full text in Research Archive
• Guttormsen, Magne Sveen; Bergholt, Lisbeth; Rekstad, John Bernhard & Tveter, Trine Spedstad (1995). Spin-dependent pre-equilibrium decay in the 163Dy(3He,α) reaction. Nuclear Physics A. ISSN 0375-9474. 589, p. 249–249. Full text in Research Archive
• Bergholt, Lisbeth; Guttormsen, Magne Sveen; Rekstad, John Bernhard; Tveter, Trine Spedstad & Sheline, R.K. (1994). K dependence in the gamma decay of neutron resonances in Ho-166. Physical Review C. Nuclear Physics. ISSN 0556-2813. 50, p. 493–496. doi: 10.1103/PhysRevC.50.493. Full text in Research Archive
• Guttormsen, Magne Sveen; Bergholt, Lisbeth; Ingebretsen, Finn; Løvhøiden, Gunnar; Messelt, Svein & Rekstad, John Bernhard [Show all 8 contributors for this article] (1994). The (3He,α) reaction mechanism. A study of the angular momentum transfer. Nuclear Physics A. ISSN 0375-9474. 573, p. 130–130. Full text in Research Archive
• Guttormsen, Magne Sveen; Rekstad, John Bernhard & al.,, - et (1994). High-spin structure of 155Dy. Nuclear Physics A. ISSN 0375-9474. 580, p. 133–133. Full text in Research Archive
• Avdeichikov, V.V.; Bergholt, Lisbeth; Guttormsen, Magne Sveen & al, [Mangler fornavn] et. (1994). Light output and energy resolution of CsI, YAG, GSO, BGO and LSO scintillators for light ions. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 349(1), p. 216–224. Full text in Research Archive
• Rekstad, John Bernhard; Tveter, Trine Spedstad; Guttormsen, Magne Sveen & Bergholt, Lisbeth (1993). K dependence in the gamma decay of neutron resonances in Er-168 and Hf-178. Physical Review C. Nuclear Physics. ISSN 0556-2813. 47, p. 2621–2634. doi: 10.1103/PhysRevC.47.2621. Full text in Research Archive
• Avdeichikov, V.V.; Bergholt, Lisbeth; Guttormsen, Magne Sveen & al., , et (1993). Light output and energy resolution of BGO and GSO scintillators for light ions. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 336(1-2). Full text in Research Archive
• Andersen, Erling; Helstrup, Håvard; Løvhøiden, Gunnar; Guttormsen, Magne Sveen; Messelt, Svein & Tveter, Trine Spedstad [Show all 7 contributors for this article] (1992). Helium-induced one-neutron transfer to levels in 162Dy. Nuclear Physics A. ISSN 0375-9474. 550, p. 235–235. Full text in Research Archive
• Guttormsen, Magne Sveen; Messelt, Svein; Ramsøy, Tore; Rekstad, John Bernhard; Tveter, Trine Spedstad & al.,, - et (1991). Gross properties of statistical γ-decay in 172Yb. Nuclear Physics A. ISSN 0375-9474. 531, p. 370–370. Full text in Research Archive
• Rekstad, John Bernhard; Tveter, Trine Spedstad & Guttormsen, Magne Sveen (1990). Chaos in nuclei and the K quantum number. Physical Review Letters. ISSN 0031-9007. 65, p. 2122–2124. doi: 10.1103/PhysRevLett.65.2122. Full text in Research Archive
• Tveter, Trine Spedstad; Guttormsen, Magne Sveen; Rekstad, John Bernhard & al.,, - et (1990). On the 171Yb(3He, α) reaction mechanism. Nuclear Physics A. ISSN 0375-9474. 516, p. 1–1. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1990). Levels, lifetimes and g-factors in 198Po and 200Po. Nuclear Physics A. ISSN 0375-9474. 509, p. 413–413. Full text in Research Archive
• Guttormsen, Magne Sveen; Rekstad, John Bernhard; Tveter, Trine Spedstad & al.,, - et (1989). Gamma decay of 172Yb after the (ρ, ρ′) inelastic reaction. Nuclear Physics A. ISSN 0375-9474. p. 255–255. Full text in Research Archive
• Tveter, Trine Spedstad; Guttormsen, Magne Sveen; Rekstad, John Bernhard & al.,, - et (1989). First-generation γ-rays from highly-excited even rare-earth nuclei. Nuclear Physics A. ISSN 0375-9474. 499, p. 100–100. Full text in Research Archive
• Guttormsen, Magne Sveen; Rekstad, John Bernhard & al., , et (1988). Particle-core multiplets in 89Y. Physica Scripta. ISSN 0031-8949. 37(843). Full text in Research Archive
• Rekstad, John Bernhard; Guttormsen, Magne Sveen & al., , et (1987). The decay of hot nuclei. Nuclear Physics A. ISSN 0375-9474. 472(269). Full text in Research Archive
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Ingebretsen, Finn; Løvhøiden, Gunnar & al.,, - et (1987). Reaction dependence and gross structure of the γ-decay of highly excited states in the rare earth nucleus 162Dy. Nuclear Physics A. ISSN 0375-9474. 470, p. 397–397. Full text in Research Archive
• Blume, K.P; Guttormsen, Magne Sveen & al.,, - et (1987). High-spin states in 163–166Hf. Nuclear Physics A. ISSN 0375-9474. 464, p. 445–445. Full text in Research Archive
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Messelt, Svein; Ramsøy, Tore; Løvhøiden, Gunnar & al.,, - et (1987). The decay of hot dysprosium nuclei. Nuclear Physics A. ISSN 0375-9474. 472, p. 269–269. Full text in Research Archive
• Ramsøy, Tore; Engeland, Torgeir; Guttormsen, Magne Sveen; Rekstad, John Bernhard; Løvhøiden, Gunnar & Vaagen, Jan S [Show all 7 contributors for this article] (1987). Particle-vibration coupled states in 161Dy. Nuclear Physics A. ISSN 0375-9474. 470, p. 79–79. Full text in Research Archive
• Guttormsen, Magne Sveen; Ramsøy, Tore & Rekstad, John Bernhard (1987). The first generation of gamma-rays from hot nuclei. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 255(3), p. 518–523. Full text in Research Archive
• Guttormsen, Magne Sveen; Ingebretsen, Finn; Messelt, Svein; Rekstad, John Bernhard & al., , et (1986). Statistical gamma decay in s-d shell nuclei. Physica Scripta. ISSN 0031-8949. 33(385). Full text in Research Archive
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Ingebretsen, Finn & al., , et (1986). Structure and decay properties of low-spin states at high excitation energy. Physica Scripta. ISSN 0031-8949. 34(644). Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1986). High-spin structure of 190–194Hg and the cranked shell model. Nuclear Physics A. ISSN 0375-9474. 453, p. 316–316. Full text in Research Archive
• Ramsøy, Tore; Rekstad, John Bernhard; Guttormsen, Magne Sveen; Ingebretsen, Finn; Løvhøiden, Gunnar & al., - et (1985). γ-decay from two-quasiparticle states populated in the 161, 163Dy(d, t). Nuclear Physics A. ISSN 0375-9474. 438, p. 301–301. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1985). High-spin structure in 169W and 170W. Nuclear Physics A. ISSN 0375-9474. 440, p. 366–366. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1985). Decay of the ground state and the 29/2+ isomer in 217Ac and g-factor measurements from perturbed α-particle angular distributions. Nuclear Physics A. ISSN 0375-9474. 436, p. 311–311. Full text in Research Archive
• Guttormsen, Magne Sveen & al., , et (1984). The second and third backbending in 194Hg. Physics Letters B. ISSN 0370-2693. 145(29). Full text in Research Archive
• Guttormsen, Magne Sveen; Rekstad, John Bernhard; Ingebretsen, Finn & al., , et (1984). Non-statistical cooling of highly excited 161Dy nucleus. Physical Review Letters. ISSN 0031-9007. 52(102). Full text in Research Archive
• Ramsøy, Tore; Rekstad, John Bernhard; Ingebretsen, Finn; Guttormsen, Magne Sveen & al.,, - et (1984). Deep-lying hole states in 145Nd. Nuclear Physics A. ISSN 0375-9474. 414, p. 269–269. Full text in Research Archive
• Guttormsen, Magne Sveen; Herbert, Hübel & al, ... et (1984). A superconducting electron spectrometer. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 227(3), p. 489–498. Full text in Research Archive
• Guttormsen, Magne Sveen & al., , et (1983). Delayed second band crossing in 170W. Physics Letters B. ISSN 0370-2693. 122(207). Full text in Research Archive
• Aasen, R.M.; Rekstad, John Bernhard; Henriquez, A.; Ingebretsen, Finn; Guttormsen, Magne Sveen & Engeland, Torgeir (1983). Gamma-ray energy dependence of transition probabilities in the continuum. Physical Review C. Nuclear Physics. ISSN 0556-2813. 28, p. 1857–1859. doi: 10.1103/PhysRevC.28.1857. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1983). Observation of the weakly deformed v i13/2 band in 188Hg. Zeitschrift für Physik A Hadrons and Nuclei. ISSN 0939-7922. 312, p. 251–251. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1983). High-spin rotational bands and pairing reduction in 166Hf. Nuclear Physics A. ISSN 0375-9474. 399, p. 199–199. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1983). The 8+, 10+, 12+ triplets in 190–196Hg. Nuclear Physics A. ISSN 0375-9474. 398, p. 119–119. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1983). Rotation aligned bands and configuration dependent interaction in 189Hg. Zeitschrift für Physik A Hadrons and Nuclei. ISSN 0939-7922. 312, p. 155–155. Full text in Research Archive
• Guttormsen, Magne Sveen (1983). Isomeric transitions in 203Bi and 205Bi. Zeitschrift für Physik A Hadrons and Nuclei. ISSN 0939-7922. 314, p. 89–89. Full text in Research Archive
• Henriquez, Adolfo; Rekstad, John Bernhard; Ingebretsen, Finn; Guttormsen, Magne Sveen; Eldhuset, Knut & Nordmoen, Bjørn [Show all 11 contributors for this article] (1983). The Decay from the two-quasiparticle regime in even-even deformed rare earth nuclei. Physics Letters B. ISSN 0370-2693. 130B(3,4), p. 171–173. Full text in Research Archive
• Guttormsen, Magne Sveen & al., - et (1982). Band crossings in weakly deformed 190Hg. Nuclear Physics A. ISSN 0375-9474. 383, p. 541–541. Full text in Research Archive
• Guttormsen, Magne Sveen & Hübel, Herbert (1982). Cranking model interpretation of weakly coupled bands in Hg isotopes. Nuclear Physics A. ISSN 0375-9474. 380, p. 502–502. Full text in Research Archive
• Guttormsen, Magne Sveen & al.,, - et (1982). Spin precession of Po in Ni detected by In-beam conversion electrons and the magnetic moment of the 15− isomer in 204Po. Zeitschrift für Physik A Hadrons and Nuclei. ISSN 0939-7922. 305, p. 1–1. Full text in Research Archive
• Guttormsen, Magne Sveen (1981). B(E2) ratios in the shape coexistent 184,186,188Hg isotopes. Physics Letters B. ISSN 0370-2693. 105(99). Full text in Research Archive
• Guttormsen, Magne Sveen & al., , et (1981). Identification of the missing rotational-aligned 12+ state in 196Hg. Physics Letters B. ISSN 0370-2693. 99(209). Full text in Research Archive
• Garrett, J.D.; Guttormsen, Magne Sveen & et, al. (1981). Evidence for Decreased Pairing Energies in Odd-N Nuclei from Band-Crossing Frequencies. Physical Review Letters. ISSN 0031-9007. 47, p. 75–78. doi: 10.1103/PhysRevLett.47.75. Full text in Research Archive
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Engeland, Torgeir; Løvhøiden, Gunnar & al.,, - et (1981). The level structure of the 153Gd nucleus studied in the 150Sm(α, n)153Gd reaction. Nuclear Physics A. ISSN 0375-9474. 371, p. 364–364. Full text in Research Archive
• Guttormsen, Magne Sveen & al., , et (1980). g-factors of high-spin isomers in 194Hg and 196Hg. Physics Letters B. ISSN 0370-2693. 97(197). Full text in Research Archive
• Riedinger, L.L.; Frauendorf, Stefan; Guttormsen, Magne Sveen & et, al. (1980). Frequency and Alignment Classification of Multiple Band Crossings. Physical Review Letters. ISSN 0031-9007. 44, p. 568–572. doi: 10.1103/PhysRevLett.44.568. Full text in Research Archive
• Guttormsen, Magne Sveen; Rekstad, John Bernhard & Riedinger, L.L. (1980). The β-Band and the Octupole Band in 152Gd. Physica Scripta. ISSN 0031-8949. 22, p. 210–210. doi: 10.1088/0031-8949/22/3/005. Full text in Research Archive
• Guttormsen, Magne Sveen; Pedersen, Torstein; Rekstad, John Bernhard; Engeland, Torgeir; Osnes, Eivind & Ingebretsen, Finn (1980). The particle-rotor model with pairing in the s-d shell: An analysis of the 23Na nucleus. Nuclear Physics A. ISSN 0375-9474. 338, p. 141–141. Full text in Research Archive
• Guttormsen, Magne Sveen; Rekstad, John Bernhard; Løvhøiden, Gunnar & al.,, - et (1980). On the ΔN = 2 coupling problem. Nuclear Physics A. ISSN 0375-9474. 334, p. 401–401. Full text in Research Archive
• Osnes, Eivind; Guttormsen, Magne Sveen & al.,, - et (1979). The Iπ = 1/2− bands in the odd-A = 19–31 nuclei. Nuclear Physics A. ISSN 0375-9474. 332, p. 1–1. Full text in Research Archive
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Engeland, Torgeir; Løvhøiden, Gunnar & al.,, - et (1979). The 153Sm nucleus: An experimental and theoretical study. Nuclear Physics A. ISSN 0375-9474. 320, p. 239–239. Full text in Research Archive
• Guttormsen, Magne Sveen; Osnes, Eivind; Rekstad, John Bernhard; Løvhøiden, Gunnar & al.,, - et (1978). Particle-rotor model description of the negative-parity states in the transitional 151Sm nucleus. Nuclear Physics A. ISSN 0375-9474. 298, p. 122–122. Full text in Research Archive

View all works in NVA

• Guttormsen, Magne Sveen; Ramsøy, Tore; Rekstad, John Bernhard & al.,, - et (1988). Level Structure of 39 89 Y, N = 50 Isotone. Springer Publishing Company. ISBN 9783540501206. 8 p. Full text in Research Archive

View all works in NVA

• Guttormsen, Magne Sveen (2025). On the Brink-Axel hypothesis. Full text in Research Archive
• Guttormsen, Magne Sveen (2025). Quasi-continuum M1 strength as function of nuclear deformation. Full text in Research Archive
• Guttormsen, Magne Sveen (2024). OSCAR and the Milan-Oslo collaboration (a story of success). Full text in Research Archive
• Guttormsen, Magne Sveen (2019). Nøytronets mørke side. Full text in Research Archive
• Guttormsen, Magne Sveen (2019). Level density in Nd isotopes as function of deformation. Full text in Research Archive
• Guttormsen, Magne Sveen (2019). Mini-workshop on the beta-Oslo method. Full text in Research Archive
• Guttormsen, Magne Sveen (2018). The beta-Oslo method. Full text in Research Archive
• Guttormsen, Magne Sveen (2017). On the validity of the generalized Brink-Axel hypothesis. Full text in Research Archive
• Guttormsen, Magne Sveen (2017). Gamma-widths, lifetimes and fluctuations in the nuclear quasi-continuum. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Midtbø, Jørgen E.; Campo, Lucia Crespo; Görgen, Andreas & Ingeberg, Vetle Wegner [Show all 11 contributors for this article] (2017). Gamma-widths, lifetimes and fluctuations in the nuclear quasi-continuum. Full text in Research Archive
• Guttormsen, Magne Sveen (2017). The beta-Oslo method. Full text in Research Archive
• Guttormsen, Magne Sveen (2016). On the validity of the Brink-Axel hypothesis. Full text in Research Archive
• Guttormsen, Magne Sveen (2016). On the validity of the generalised Brink-Axel hypothesis. Full text in Research Archive
• Guttormsen, Magne Sveen (2016). Nuclear structure in the quasi-continuum. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Görgen, Andreas; Renstrøm, Therese; Siem, Sunniva & Tornyi, Tamas Gabor [Show all 7 contributors for this article] (2016). Is the generalized Brink-Axel hypothesis valid? Full text in Research Archive
• Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 23 contributors for this article] (2016). The Statistical Properties Of 92Mo And Implications For The p-process. Full text in Research Archive Show summary

  A particularly challenging part of the question of how elements heavier than iron are created in extreme, astrophysical environments is the creation of the so-called p-nuclei, which are believed to be mainly produced in the O-Ne layer of type II supernovae or type Ia supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions for the production of these isotopes. Astrophysical model calculations are able to reproduce abundance patterns of most p-isotopes reasonably well, with some pivotal exceptions. In particular, p-isotopes of mass 92 ≤ A ≤ 98 are underproduced in calculations compared to the actual abundance of these isotopes. The p-isotope 92Mo represents one of the most severe cases of underproduction. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. The main destruction mechanism of this isotope in the standard description of the p-process is through the 92Mo(γ, p)91Nb reaction. Measurements on the nuclear level density and average gamma strength function of 92Mo have been carried out at the Oslo Cyclotron Laboratory. TALYS cross section and reaction rate calculations where the experimental results are used as input will be presented. The data provide stringent constraints on the 91Nb(p, γ)92Mo (and consequently the inverse) reaction rate. The reaction rate extracted in this work was used in reaction network calculations for the scenario of a p-process taking place in a type II supernova explosion as the shock front passes through the O-Ne layer of a 25 solar mass star.

• Guttormsen, Magne Sveen (2015). My projects in CAN. Full text in Research Archive
• Guttormsen, Magne Sveen (2015). Thermodynamic and electromagnetic properties of nuclei. Full text in Research Archive
• Guttormsen, Magne Sveen (2015). The standard Oslo method. Full text in Research Archive
• Guttormsen, Magne Sveen (2015). Scissors resonances in the quasi-continuum of heavy nuclei. Full text in Research Archive
• Guttormsen, Magne Sveen (2015). Adam's Early Era at HMI, Berlin. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Blasi, N; Bracco, A; Camera, F & Eriksen, Tomas Kvalheim [Show all 19 contributors for this article] (2014). Recent results using large LaBr3 detectors and future perspectives. Full text in Research Archive
• Guttormsen, Magne Sveen (2014). Basics of the Oslo Method on the beta-stability line. Full text in Research Archive
• Tveten, Gry Merete; Campo, L.C.; Eriksen, Tomas Kvalheim; Giacoppo, Francesca; Guttormsen, Magne Sveen & Görgen, Andreas [Show all 17 contributors for this article] (2014). The statistical properties of Sn-isotopes studied with the Oslo-method. Full text in Research Archive
• Guttormsen, Magne Sveen (2014). Nuclear level densities from an experimental point of view. Full text in Research Archive
• Guttormsen, Magne Sveen (2014). Exploring the Nuclear Quasi-Continuum with the Oslo Method. Full text in Research Archive
• Guttormsen, Magne Sveen (2014). The long and winding road of the Oslo Method. Full text in Research Archive
• Guttormsen, Magne Sveen (2014). Large Scissors Resonance Strength in Actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2014). Level density of atomic nuclei. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). Level densities and the scissors resonance in Th, Pa and U isotopes. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). The Oslo Method. Full text in Research Archive
• Guttormsen, Magne Sveen; Bernstein, Lee; Bürger, Alexander; Görgen, Andreas; Gunsing, Frank & Hagen, Trine Wiborg [Show all 11 contributors for this article] (2013). Scissors strength in the quasi-continuum of actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). The Oslo method applied to the actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). Observation of large scissors strength in actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). Constant-temperature level densities and large scissors strength in the quasi- continuum of actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). Scissors mode in the actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2013). The Oslo Cyclotron Laboratory and level density and gamma-strength in the actinides. Full text in Research Archive
• Guttormsen, Magne Sveen; Bernstein, Lee; Bürger, Alexander; Görgen, Andreas; Gunsing, Frank & Hagen, Trine Wiborg [Show all 11 contributors for this article] (2012). Observation of large orbital scissors strength in actinides. Full text in Research Archive
• Guttormsen, Magne Sveen (2012). Large scissors strength in the quasi-continuum of actinides. Full text in Research Archive
• Larsen, Ann-Cecilie; Bürger, Alexander; Goriely, Stephane; Guttormsen, Magne Sveen; Görgen, Andreas & Harrisopulos, Sotirios [Show all 13 contributors for this article] (2012). LOW-ENERGY ENHANCEMENT IN THE γ STRENGTH WITH IMPACT ON ASTROPHYSICAL REACTION RATES. Full text in Research Archive
• Larsen, Ann-Cecilie; Bürger, Alexander; Goriely, Stephane; Guttormsen, Magne Sveen; Görgen, Andreas & Harrisopulos, Sotirios [Show all 13 contributors for this article] (2012). Astrophysical reaction rates and the low-energy enhancement in the γ-ray strength. Full text in Research Archive
• Larsen, Ann-Cecilie; Bürger, Alexander; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen & Hagen, Trine Wiborg [Show all 29 contributors for this article] (2011). Experiments of reaction model inputs: level density and gamma strength. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Bürger, Alexander; Eriksen, Tomas Kvalheim; Görgen, Andreas & Hagen, Trine Wiborg [Show all 16 contributors for this article] (2011). Level density and gamma strength - achievements and challenges. Full text in Research Archive
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander; Görgen, Andreas; Nyhus, Hilde-Therese & Siem, Sunniva [Show all 9 contributors for this article] (2011). Do light nuclei display a universal gamma-ray strength function? Full text in Research Archive
• Bürger, Alexander; Görgen, Andreas; Guttormsen, Magne Sveen; Hagen, Trine Wiborg; Larsen, Ann-Cecilie & Mansouri, Pejman [Show all 15 contributors for this article] (2010). Level Densities and Gamma-Ray Strength Functions in Zr Isotopes. Full text in Research Archive
• Olsen, Dag Rune & Guttormsen, Magne Sveen (2010). Kreftbehandling og protonterapi. [TV]. NRK Schrødingers katt. Full text in Research Archive
• Bürger, Alexander; Larsen, Ann-Cecilie; Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Nyhus, Hilde-Therese & Siem, Sunniva [Show all 7 contributors for this article] (2010). Level Densities and γ Strength Functions in Light Sc and Ti Isotopes. Proceedings of Science (PoS). doi: 10.1051/epjconf/20100203003. Full text in Research Archive
• Bürger, Alexander; Larsen, Ann-Cecilie; Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Nyhus, Hilde-Therese & Siem, Sunniva [Show all 16 contributors for this article] (2009). Level Densities and Gamma Strength Functions in Light Sc and Ti Isotopes. Full text in Research Archive Show summary

  Level densities and γ-ray strength functions are an important input to stellar reaction models and isotope abundance calculations. The nuclear physics group at the Oslo Cyclotron Laboratory has developed a method to extract both the level density and the γ-ray strength function below the particle-emission thresholds from particle-γ coincidence data obtained in proton- or 3 He-induced pickup or transfer reactions. This experimental method will be presented in the talk. The method has recently been applied to study the nuclei 43 Sc and 44,45,46 Ti using the reactions 46 Ti(p,x γ)X. In 45 Ti, steps in the level density as a function of excitation energy have been observed. The nucleus 44 Ti is expected to be exclusively produced in supernovae. The abundance observed is therefore regarded as a marker for the type of supernova. The nuclear level density of 44 Ti is an important input for modelling the production of 44 Ti in the stellar environment. Preliminary results on level densities and γ-ray strength functions for 43 Sc and 44,45,46 Ti will be presented.

• Toft, Heidi Kristine; Bürger, Alexander; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Nyhus, Hilde-Therese & Siem, Sunniva [Show all 8 contributors for this article] (2009). Level Densities and Gamma Strength Functions in 116,118,118Sn. Full text in Research Archive
• Nyhus, Hilde-Therese; Siem, Sunniva; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Syed, Naeem Ul Hasan & Voinov, Alexander (2009). Level densities and the gamma ray strength functions of 163;164Dy. Full text in Research Archive
• Toft, Heidi Kristine; Bürger, Alexander; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Nyhus, Hilde-Therese & Siem, Sunniva [Show all 8 contributors for this article] (2009). Level Densities and Gamma Strength Functions in 116,118,119Sn. Full text in Research Archive
• Bürger, Alexander; Syed, Naeem Ul Hasan; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Harissopulos, Sotirios & Kmiecik, M. [Show all 16 contributors for this article] (2009). Level Densities and Strength Functions in Light Sc and Ti Isotopes. Full text in Research Archive
• Bürger, Alexander; Larsen, Ann-Cecilie; Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Harissopulos, Sotirios & Kmiecik, Marysia [Show all 16 contributors for this article] (2009). Level density and gamma-ray strength function in 43Sc. Full text in Research Archive
• Guttormsen, Magne Sveen (2008). Nuclear level density and its thermodynamical interpretation. Full text in Research Archive
• Nyhus, Hilde-Therese; Siem, Sunniva; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bürger, Alexander & Syed, Naeem Ul Hasan [Show all 9 contributors for this article] (2008). Level Densities, Thermodynamics and Gamma-ray Strength Functions in 163,164Dy. Full text in Research Archive
• Guttormsen, Magne Sveen (2008). Physics at SAFE: Level density and thermodynamics of warm nuclei. Full text in Research Archive
• Guttormsen, Magne Sveen (2008). Finn Ingebretsen 70 år. Full text in Research Archive
• Guttormsen, Magne Sveen (2008). Protonterapi. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne Sveen; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard & Syed, Naeem Ul Hasan [Show all 10 contributors for this article] (2007). Level densities and gamma-strength functions in rare earth nuclei. Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Brune, C.R.; Guttormsen, Magne Sveen; Massey, T.N. & Schiller, Andreas [Show all 7 contributors for this article] (2007). Experimental Study of Level Density and gamma-strength Functions from Compound Nuclear Reactions. Full text in Research Archive
• Larsen, Ann-Cecilie; Chankova, Rositsa; Guttormsen, Magne Sveen; Ingebretsen, Finn; Lönnroth, Tom & Messelt, Svein [Show all 11 contributors for this article] (2007). Puzzling gamma-ray strength functions in 44,45Sc and 50,51V. Full text in Research Archive
• Guttormsen, Magne (2007). Nuclear Physics at the Oslo Cyclotron Laboratory. Full text in Research Archive Show summary

  The low energy nuclear physics group has developed a method for measuring level density and photon strength functions in the continuum. These quantities are known from conventional nuclear spectroscopy near the ground state, but are little known at higher excitation energies. The instrumentation and methods will be briefly described. New and controversial experimental results using the Oslo method will also be presented.

• Guttormsen, Magne Sveen (2007). Syklotronlaboratoriet og protonterapi. Full text in Research Archive
• Guttormsen, Magne; Chankova, Rositsa; Schiller, Andreas; Siem, Sunniva; Sunde, Ann-Cecilie & Syed, Naeem Ul Hasan [Show all 8 contributors for this article] (2006). Nuclear level densities. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Schiller, Andreas & Ødegård, Stein Westad [Show all 9 contributors for this article] (2006). Level densities and gamma-ray strength functions in Sm isotopes. Full text in Research Archive
• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard & Schiller, Andreas [Show all 9 contributors for this article] (2006). Entropy in Nuclei. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Syed, Naeem Ul Hasan & Schiller, Andreas [Show all 8 contributors for this article] (2006). Level densities and gamma-ray strength functions in Sm isotopes. Full text in Research Archive
• Larsen, Ann-Cecilie; Guttormsen, Magne; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom & Messelt, Svein [Show all 12 contributors for this article] (2006). Radiative strength functions of warm nuclei in the 1f7/2 shell. Full text in Research Archive
• Schiller, Andreas; Voinov, Alexander; Agvaanluvsan, Undraa; Algin, Emel; Becker, J.A. & Belgya, Thomas [Show all 15 contributors for this article] (2005). Soft radiative strength in warm nuclei. Full text in Research Archive
• Algin, Emel; Schiller, Andreas; Voinov, Alexander; Agvaanluvsan, Undraa; Belgya, Thomas & Bernstein, Lee [Show all 15 contributors for this article] (2005). Level densities and radiative strength functions in 56,57Fe and 96,97Mo. Full text in Research Archive
• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Hjorth-Jensen, Morten; Rekstad, John Bernhard & Schiller, Andreas [Show all 10 contributors for this article] (2005). Single particle entropy in heated nuclei. Full text in Research Archive
• Voinov, Alexander; Grimes, S.M.; Agvaanluvsan, Undraa; Algin, Emel; Belgya, Thomas & Brune, C.R. [Show all 13 contributors for this article] (2005). Level densities of iron isotopes and lower-energy enhancement of gamma-strength function. Full text in Research Archive
• Algin, Emel; Schiller, Andreas; Voinov, Alexander; Agvaanluvsan, Undraa; Belgya, Thomas & Chankova, Rositsa [Show all 12 contributors for this article] (2005). Level densities and radiative strength functions. Full text in Research Archive
• Rekstad, John Bernhard; Siem, Sunniva; Guttormsen, Magne & Ingebretsen, Finn (2005). Syklotronlaboratoriet i Oslo, et senter for forskning og knoppskyting i 25 år. Fra Fysikkens Verden. ISSN 0015-9247. p. 35–39. Full text in Research Archive
• Sunde, Ann-Cecilie; Chankova, Rosita; Guttormsen, Magne; Ingebretsen, Finn; Lönnroth, Tom & Messelt, Svein [Show all 11 contributors for this article] (2004). Thermal and electromagnetic properties in the light vanadium isotopes 50,51V. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Rekstad, John Bernhard; Chankova, Rosita & Sunde, Ann-Cecilie (2004). Study of the level density and gamma strength function using MINIBALL. Full text in Research Archive
• Lønnroth, Tom & Guttormsen, Magne (2004). Hur attrahera studerande till fysikstudier och ge dem en interessant undervisning? Full text in Research Archive
• Guttormsen, Magne; Chankova, Rosita; Hjorth-Jensen, Morten; Ingebretsen, Finn; Messelt, Svein & Rekstad, John Bernhard [Show all 11 contributors for this article] (2004). Heated nuclei and radiative strength functions. Full text in Research Archive
• Chankova, Rosita; Guttormsen, Magne; Sunde, Ann-Cecilie; Ingebretsen, Finn; Lønnroth, Tom & Messelt, Svein [Show all 11 contributors for this article] (2004). Level density and gamma-decay properties of heated 93-98Mo isotopes. Full text in Research Archive
• Schiller, Andreas; Voinov, Alexander; Agvaanluvsan, Undraa; Algin, Emel; Becker, J.A. & Bernstein, Lee [Show all 13 contributors for this article] (2004). Soft radiative strength in warm nuclei. Full text in Research Archive
• Sunde, Ann-Cecilie; Guttormsen, Magne; Chankova, Rosita; Ingebretsen, Finn; Lønnroth, Tom & Rekstad, John Bernhard [Show all 10 contributors for this article] (2004). Level density and gamma-ray strength in 50,51V. Full text in Research Archive
• Siem, Sunniva; Algin, Emel; Agvaanluvsan, Undraa; Guttormsen, Magne; Chankova, Rosita & Ingebretsen, Finn [Show all 13 contributors for this article] (2004). Entropy in hot nuclei. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne & Rekstad, John Bernhard (2003). Thermodynamic and electromagnetic properties of nuclei. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Rekstad, John Bernhard; Chankova, Rositsa; Schiller, Andreas & Sunde, Ann-Cecilie (2003). Level densities and gamma strength functions. Full text in Research Archive
• Schiller, Andreas; Becker, J.A.; Bernstein, Lee; Voinov, Alexander; Guttormsen, Magne & Hjorth-Jensen, Morten [Show all 11 contributors for this article] (2003). Thermal aspects of the nuclear pairing process. Full text in Research Archive
• Bagheri, Assadollah; Chankova, Rositsa; Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn & Messelt, Svein [Show all 12 contributors for this article] (2003). Electromagnetic and thermodynamic proprties of rare earth nuclei. Full text in Research Archive
• Agvaanluvsan, Undraa; Schiller, Andreas; Becker, J.A.; Bernstein, Lee; Guttormsen, Magne & Mitchell, Gary [Show all 9 contributors for this article] (2003). Level densities and radiative strength functions in 170,171Yb. Full text in Research Archive
• Algin, Emel; Becker, J.A.; Bernstein, Lee; Garrett, P.E.; Guttormsen, Magne & Mitchell, Gary [Show all 11 contributors for this article] (2003). Thermodynamical Properties of 56Fe. Full text in Research Archive
• Voinov, Alexander; Schiller, Andreas; Guttormsen, Magne; Rekstad, John Bernhard & Siem, Sunniva (2003). Electromagnetic character of soft dipole modes in rare earth nuclei. Full text in Research Archive
• Voinov, Alexander; Schiller, Andreas; Becker, J.A.; Bernstein, Lee; Garrett, P.E. & Guttormsen, Magne [Show all 11 contributors for this article] (2003). Nature of the pygmy resonance in continuous gamma-spectra. Full text in Research Archive
• Algin, Emel; Becker, J.A.; Bernstein, Lee; Garrett, P.E.; Guttormsen, Magne & Mitchell, Gary [Show all 11 contributors for this article] (2003). Average Nuclear Level Densities and Radiative Strength Functions in 56,57Fe from Primary Gamma-Ray Spectra. Full text in Research Archive
• Lønnroth, Tom; Guttormsen, Magne; Chankova, Rositsa; Sunde, Ann-Cecilie; Schiller, Andreas & Voinov, Alexander (2003). Light Nuclei at High Excitation: Study of Level Densities at Alpha-Cluster Energies. Full text in Research Archive
• Lønnroth, Tom; Guttormsen, Magne; Chankova, Rositsa; Melby, Elin; Rekstad, John Bernhard & Schiller, Andreas [Show all 8 contributors for this article] (2003). Level Densities and Gamma-Ray Strength in Light Nuclei. Full text in Research Archive
• Guttormsen, Magne; Hjorth-Jensen, Morten; Rekstad, John Bernhard; Siem, Sunniva; Schiller, Andreas & Voinov, Alexander (2003). MEASUREMENTS OF NUCLEAR LEVEL DENSITIES AND GAMMA-RAY STRENGTH FUNCTIONS AND THEIR INTERPRETATIONS. Full text in Research Archive
• Schiller, Andreas; Bernstein, Lee; Cooper, Jason; Becker, J.A.; Algin, Emel & McMahan, M.A. [Show all 13 contributors for this article] (2002). The STARS array. Full text in Research Archive
• Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Rekstad, John Bernhard & Siem, Sunniva (2002). Caloric curves of nuclei. Full text in Research Archive
• Schiller, Andreas; Bernstein, Lee; Voinov, Alexander; Guttormsen, Magne; Hjorth-Jensen, Morten & Rekstad, John Bernhard [Show all 9 contributors for this article] (2002). Radiative strength functions and level densities. Full text in Research Archive
• Guttormsen, Magne; Hjorth-Jensen, Morten; Rekstad, John Bernhard; Siem, Sunniva; Schiller, Andreas & Voinov, Alexander (2002). Measurements of Nuclear Level Densities and Gamma-Ray Strength Functions and their Interpretations. Full text in Research Archive Show summary

  A method to extract primary $\gamma$-ray spectra from particle-$\gamma$ coincidences at excitation energies up to the neutron binding energy is described. From these spectra, the level density and $\gamma$-ray strength function can be determined. From the level density, several thermodynamical quantities are obtained within the microcanonical and canonical ensemble. Also models for the $\gamma$-ray strength function are discussed.

• Guttormsen, Magne; Rekstad, John Bernhard; Siem, Sunniva; Schiller, Andreas & Voinov, Alexander (2002). Extraction of level densities from primary gamma-spectra. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Rekstad, John Bernhard; Schiller, Andreas & Voinov, Alexander (2002). Level densities and gamma strength functions: important quanteties in nucleosynthesis. Full text in Research Archive
• Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva [Show all 7 contributors for this article] (2001). Level density, thermodynamics and radiative strength. Full text in Research Archive Show summary

  A method to measure level density (LD) and radiative strength (RS) below the particle threshold with previously unachieved accuracy has been developed. Using the (^3He,\alpha\gamma) reaction on rare earth nuclei at the Oslo Cyclotron Laboratory, the resulting LD and RS have been successful in describing (\gamma,\gamma') reaction cross-sections and total \gamma spectra following n capture, thereby verifying the unexpected resonant structure at 3~MeV in the RS, also observed by Igashira et al\rm. Since the LD essentially equals the \mu-canonical partition function (PF), temperature and heat capacity can be determined. Structures in these quantities have been related to Cooper-pair breaking. Laplace transformation of the LD yields the canonical PF. The shape of the canonical C_V(T) curve indicates quenching of pairing correlations at finite T, as predicted by Sano/ Yamasaki, Goodman and Tanabe/Sugawara-Tanabe long ago. New results and the possibility of a pairing phase transition are discussed.

• Tavukcu, Emel; Mitchell, Gary; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva [Show all 9 contributors for this article] (2001). Bulk properties of ^56Fe. Full text in Research Archive Show summary

  A technique to extract primary (first generation) \gamma rays has been developed by the Oslo Cyclotron group. The primary \gamma-ray spectrum represents the \gamma decay probability distribution, and it depends on the product of the level density at the final excitation energy and the radiative strength function, according to the Brink-Axel hypothesis. Within an iterative procedure, the level density and the radiative strength function can be extracted from the primary \gamma-ray spectra. The method has been applied to study ^56Fe which is close to a doubly magic core. The experiment was carried out with a 45-MeV ^3He beam using the (^3He,\alpha) reaction on a ^57Fe target at the Oslo Cyclotron Laboratory. New results of this experiment will be discussed.

• Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva (2001). Level density and thermal properties in rare earth nuclei. Full text in Research Archive
• Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2001). Thermal quenching of pair correlations in rare earth nuclei. Full text in Research Archive Show summary

  The gamma-ray spectra of the (3He,alpha gamma) pick-up reaction on 162,163Dy and 172,173Yb are utilized to extract level densities. The temperature T as function of excitation energy E is deduced within the microcanonical ensemble. Oscillations in T(E) are interpreted as the breaking of Cooper pairs. The deduced heat capacity in the canonical ensemble shows an S-form indicating a critical temperature for quenching of pair correlations at Tc = 0.50(4) MeV.

• Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard; Schiller, Andreas & Siem, Sunniva (2001). Single quasiparticle entropy in excited nuclei with T < 1MeV. Full text in Research Archive Show summary

  Entropies in rare earth nuclei are extracted from measured level densities. The entropy difference between odd and even-even mass nuclei are almost independent of excitation energy in the 1.5 - 6 MeV region. A global study of level densities from so-called anchor points, reveals that this is a common property for mid-shell nuclei. The findings indicate thermodynamical extensivity, suggesting that each thermal quasiparticle is carrying an entropy of appr. S = 2.

• Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard & Siem, Sunniva (2001). Thermodynamical properties of rare earth nuclei: the melting of pair correlations. Full text in Research Archive
• Schiller, Andreas; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard; Siem, Sunniva & Voinov, Alexander (2001). Radiative strength function in deformed rare earth nuclei below the neutron binding energy. Full text in Research Archive
• Tavukcu, Emel; Bernstein, Lee; Guttormsen, Magne; Melby, Elin; Mitchell, Gary & Rekstad, John Bernhard [Show all 8 contributors for this article] (2001). Thermodynamical properties of 56Fe. Full text in Research Archive
• Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn; Melby, Elin; Messelt, Svein & Rekstad, John Bernhard [Show all 9 contributors for this article] (2001). Thermodynamical properties in rare earth nuclei. Full text in Research Archive Show summary

  The Oslo Cyclotron Group has established a method to extract primary gamma-ray spectra at excitation energies up to the neutron binding energy. From these energy distributions, the level density and gamma-ray strength function can be extracted. In this group report we focus on experimental thermodynamical quantities obtained within the microcanonical and canonical ensemble theory.

• Siem, Sunniva; Schiller, Andreas; Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin & Rekstad, John Bernhard (2000). Level density and thermal properties in rare earth nuclei. Full text in Research Archive
• Guttormsen, Magne (2000). Thermodynamical properties of excited nuclei with T < 1MeV. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Hjorth-Jensen, Morten; Melby, Elin; Rekstad, John Bernhard & Schiller, Andreas (2000). Level densities and the thermal quenching of pair correlations in rare earth nuclei. Full text in Research Archive
• Siem, Sunniva; Guttormsen, Magne; Ingeberg, Kristian; Melby, Elin; Rekstad, John Bernhard & Schiller, Andreas (2000). Thermal quenching of pair correlations and gamma-strength functions in 148,149Sm. Full text in Research Archive
• Schiller, Andreas; Bergholt, Lisbeth; Guttormsen, Magne; Melby, Elin; Messelt, Svein & Rekstad, John Bernhard [Show all 7 contributors for this article] (1999). Level density in 162-Dy. Full text in Research Archive
• Siem, Sunniva; Bergholt, Lisbeth; Guttormsen, Magne; Melby, Elin; Rekstad, John Bernhard & Schiller, Andreas [Show all 7 contributors for this article] (1999). On level densities in rare earth nuclei. Full text in Research Archive
• Schiller, Andreas; Bergholt, Lisbeth; Guttormsen, Magne; Melby, Elin; Messelt, Svein & Rekstad, John Bernhard [Show all 7 contributors for this article] (1999). Level density and gamma-strength functions in rare earth nuclei. Full text in Research Archive
• Melby, Elin; Bergholt, Lisbeth; Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn & Messelt, Svein [Show all 10 contributors for this article] (1999). Experimental temperature and heat capacity in rare earth nuclei. Full text in Research Archive
• Guttormsen, Magne (1999). Observation of thermodynamical properties in rare earth nuclei. Full text in Research Archive
• Lonnroth, Tom; Kallman, K.; Guttormsen, Magne; Bergholt, Lisbeth; Bjerve, Amund & Ingeberg, Kristian [Show all 8 contributors for this article] (1999). Spectroscopy with entry-state selection: Search for cluster-state gamma-ray emission. Full text in Research Archive
• Lonnroth, Tom; Guttormsen, Magne & Schiller, Andreas (1999). New observation methods for alpha-particle elastic scattering. Microscopic properties of alpha cluster states. Full text in Research Archive
• Rekstad, John Bernhard; Bergholt, Lisbeth; Guttormsen, Magne; Hjorth-Jensen, Morten; Ingebretsen, Finn & Melby, Elin [Show all 10 contributors for this article] (1999). Measurements of level densities and gamma ray strength functions. Full text in Research Archive
• Guttormsen, Magne; Bergholt, Lisbeth; Hjorth-Jensen, Morten; Ingebretsen, Finn; Melby, Elin & Messelt, Svein [Show all 10 contributors for this article] (1999). Level density extraction technique and applications. Full text in Research Archive
• Greenless, P.T.; Guttormsen, Magne; Messelt, Svein; Schiller, Andreas; Siem, Sunniva & Tveter, Trine Spedstad (1999). Identification of excited states in <SUP>226</SUP>U. Full text in Research Archive
• Melby, Elin; Bergholt, Lisbeth; Guttormsen, Magne; Huseby, I.; Rekstad, John Bernhard & Schiller, Andreas [Show all 8 contributors for this article] (1999). K-selection in gamma-decay after ARC and thermal neutron capture. Full text in Research Archive
• Melby, Elin; Bergholt, Lisbeth; Guttormsen, Magne; Messelt, Svein; Rekstad, John Bernhard & Schiller, Andreas [Show all 7 contributors for this article] (1999). Varme kjerner. Full text in Research Archive
• Melby, Elin; Bergholt, Lisbeth; Guttormsen, Magne; Messelt, Svein; Rekstad, John Bernhard & Schiller, Andreas [Show all 7 contributors for this article] (1999). New Measurements of Level Densities. Full text in Research Archive
• Chankova, Rosita & Guttormsen, Magne (2006). Statistical concepts applied in structure studies of warm nuclei. Universitetet i Oslo. Full text in Research Archive
• Lønnroth, Tom; Linden, Johan; Kallman, Kjell-Mikael & Guttormsen, Magne Sveen (2006). Hur attrahera studerande till fysikstudier och ge dem en interessant undervisning? Pedagogiske fakulteten. ISSN 9789521216671. Full text in Research Archive
• Schiller, Andreas; Voinov, Alexander; Algin, Emel; Becker, J.A.; Bernstein, Lee & Garrett, P.E. [Show all 10 contributors for this article] (2004). Establishment of M1 multipolarity of a 6.5 mu_N^2 resonance in 172-Yb at E_gamma=3.3 MeV. Los Alamos preprint server, http://xxx.lanl.gov/abs/nucl-ex/0401038. Full text in Research Archive

View all works in NVA