Eda Sahin

• Pedersen, Line Gaard; Sahin, Eda; Görgen, Andreas; Garrote, Frank Leonel Bello; Tsunoda, Y. & Otsuka, T. [Vis alle 67 forfattere av denne artikkelen] (2026). Evolution of the nuclear structure in neutron-rich Cu isotopes: first spectroscopy of odd-odd $$^{74}$$Cu and $$^{76}$$Cu. European Physical Journal A. ISSN 1434-6001. 62(6). doi: 10.1140/epja/s10050-026-01873-w. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Excited states in the odd-odd isotopes $$^{74}$$ 74 Cu and $$^{76}$$ 76 Cu were observed for the first time in a spectroscopic study following the $$\beta $$ β decay of $$^{74}$$ 74 Ni and $$^{76}$$ 76 Ni. The experiment was performed at the Radioactive Isotope Beam Factory at RIKEN Nishina Center using the EURICA setup and the BigRIPS separator. Level schemes were constructed based on the analysis of $$\gamma $$ γ - $$\gamma $$ γ coincidences. The time correlations between $$\beta $$ β and $$\gamma $$ γ decay showed no evidence for population of isomeric states in either nucleus. The experimental results are compared to large-scale Monte Carlo shell-model calculations with the A3DA-m interaction. The low-lying states in $$^{74}$$ 74 Cu and $$^{76}$$ 76 Cu are interpreted as spin multiplets arising from the coupling of an odd proton in the $$2p_{3/2}$$ 2 p 3 / 2 or $$1f_{5/2}$$ 1 f 5 / 2 orbital with an odd neutron in the $$1g_{9/2}$$ 1 g 9 / 2 or $$2p_{1/2}$$ 2 p 1 / 2 orbital. The results provide information on the evolution of single-particle orbitals along the chain of neutron-rich Cu isotopes and on the proton-neutron interaction in the vicinity of $$^{78}$$ 78 Ni, which serve as important benchmarks for shell-model calculations. The non-observation of the low-energy isomeric state at 65 keV in $$^{76}$$ 76 Cu, combined with the observed decay pattern from higher-lying states, strongly supports a spin-parity assignment of $$3^{(-)}$$ 3 ( - ) for the ground state and ( $$6^{-}$$ 6 - ) for the isomeric state, resolving a long-standing ambiguity discussed in previous studies.

• Markova, Maria; Larsen, Ann-Cecilie; Neumann-Cosel, P. von; Litvinova, E.; Goriely, S. & Bell, Lauren Tracy [Vis alle 17 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Heines, J. S.; Modamio, Victor; Görgen, A.; Korten, W.; Clément, E. & Dudouet, J. [Vis alle 29 forfattere av denne artikkelen] (2026). Triaxiality of neutron-rich ruthenium nuclei studied by lifetime measurements. European Physical Journal A. ISSN 1434-6001. 62(3). doi: 10.1140/epja/s10050-025-01782-4. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The breaking of axial symmetry in nuclei enables otherwise precluded behaviours, making it an interesting phenomenon to study. Experimental fingerprints such as very low-lying $$2_2^+$$ 2 2 + states suggest pronounced triaxial deformation for the neutron-rich ruthenium isotopes. Nevertheless, theoretical calculations differ in the description of the triaxial deformation and its evolution with neutron number, making experimental data crucial to understanding it. We investigated the evolution of the degree of triaxiality and $$\gamma $$ γ rigidity in neutron-rich ruthenium isotopes by measuring lifetimes of excited states in $$^{108-112}$$ 108 - 112 Ru with the recoil distance Doppler-shift method. The experiment was carried out at the Grand Accélérateur National d’Ions Lourds using the Advanced Gamma Tracking Array coupled to the Variable Mode Spectrometer. We obtained B ( E 2) values for 29 transitions in the studied nuclei and compared them with fully microscopic symmetry conserving configuration mixing calculations, and phenomenological generalized triaxial rotor and triaxial particle-rotor models. The models generally reproduce the measured transition strengths, and show an increase in triaxiality with neutron number, reaching near maximum triaxiality in $$^{112}$$ 112 Ru. The results are consistent with a transition from $$\gamma $$ γ  soft to $$\gamma $$ γ  rigid motion as the neutron number increases.

• Moon, B.; Lee, J.; Jang, Y.; Watanabe, H.; Nishimura, S. & Phong, V. [Vis alle 41 forfattere av denne artikkelen] (2026). Commissioning and performance of IDATEN: A large fast-timing γ-ray detector array at the RIBF. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 1084. doi: 10.1016/j.nima.2025.171239. Fulltekst i vitenarkiv
• Begala, M.; Sohler, D.; Elekes, Z.; Juhász, M. M.; Utsuno, Y. & Otsuka, T. [Vis alle 87 forfattere av denne artikkelen] (2025). EXCITED STATES IN THE NEUTRON RICH NUCLEI 46S AND 47S. Acta Physica Polonica B, Proceedings Supplement. ISSN 1899-2358. 18(2). doi: 10.5506/APhysPolBSupp.18.2-A17. Fulltekst i vitenarkiv Vis sammendrag

  Data on the structure of sulphur isotopes close to the neutron drip-line are rather scarce. The excited states of the very neutron-rich 46S and 47S nuclei have been investigated by in-beam gamma-ray spectroscopy at the Radioactive Isotope Beam Factory at the RIKEN Nishina Center. After multi-nucleon knockout reactions on the liquid-hydrogen MINOS target, the 2+1 → 0+1 gamma transition of 46S, already reported in literature, has been confirmed. Additionally, two new gamma rays have been assigned to this isotope and one gamma line has been observed in 47S.

• Piętka, I. Z.; Wrzosek-Lipska, K.; Garrett, P. E.; Zielińska, M.; Próchniak, L. & Nannini, A. [Vis alle 94 forfattere av denne artikkelen] (2025). PROBING LOW-ENERGY STATES IN¹¹⁰Cd USING COULOMB EXCITATION. Acta Physica Polonica B, Proceedings Supplement. ISSN 1899-2358. 18(2). doi: 10.5506/APhysPolBSupp.18.2-A26. Fulltekst i vitenarkiv Vis sammendrag

  A campaign of Coulomb-excitation experiments to study the electromagnetic structure of 110Cd was performed using beams of 14N, 32S, and 60Ni. The use of various reaction partners enables disentangling the contributions of individual electromagnetic matrix elements involved in the excitation process, yielding, among others, a precise determination of the lifetime of the 2+2 state in 110Cd.

• Heines, Johannes Sørby; Modamio, Victor; Görgen, Andreas; Korten, Wolfram; Ljungvall, Joa & Pasqualato, G. [Vis alle 45 forfattere av denne artikkelen] (2025). NEW LIFETIME MEASUREMENTS IN THE RUTHENIUM CHAIN: INVESTIGATING THE EVOLUTION OF TRIAXIALITY. Acta Physica Polonica B, Proceedings Supplement. ISSN 1899-2358. 18(2). doi: 10.5506/APhysPolBSupp.18.2-A22. Fulltekst i vitenarkiv Vis sammendrag

  We have used the recoil distance Doppler-shift method to measure lifetimes of excited states in 108Ru, 110Ru, and 112Ru. Excited states in these nuclei were populated by fusion–fission reactions between a 238U beam and a 9Be target in an experiment at GANIL. Fission fragments were identified event by event in the VAMOS++ spectrometer, while γ-rays were detected by the Advanced Gamma Tracking Array (AGATA). The lifetimes in the ground state band are consistent with rotational structures and constant B(E2) values indicate that the deformation does not change significantly across the chain of studied ruthenium nuclei. Preliminary results for lifetimes of states in the γ-band indicate a well deformed triaxial shape with a γ parameter close to 30◦ in 110Ru, with a slight change towards oblate deformation in 112Ru.

• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Vis alle 15 forfattere av denne artikkelen] (2025). Remeasuring the γ-decay branching ratio of the Hoyle state. Physical Review C. ISSN 2469-9985. 112. doi: 10.1103/2h2s-sbyx. Fulltekst i vitenarkiv
• Enciu, M.; Obertelli, A.; Doornenbal, P.; Heinz, M.; Miyagi, T. & Nowacki, F. [Vis alle 81 forfattere av denne artikkelen] (2024). Spectroscopy of K 52. Physical Review C. ISSN 2469-9985. 110(6). doi: 10.1103/PhysRevC.110.064301. Fulltekst i vitenarkiv Vis sammendrag

  The first spectroscopy of 52 K was investigated via in-beam 𝛾-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory after one-proton and one-neutron knockout from 53 Ca and 53 K beams impinging on a 15-cm liquid hydrogen target at ≈230 MeV/nucleon. The energy level scheme of 52 K was built using single 𝛾 and 𝛾−𝛾 coincidence spectra. The spins and parities of the excited states were established based on momentum distributions of the fragment after the knockout reaction and based on exclusive cross sections. The results were compared to state-of-the-art shell model calculations with the SDPF-Umod interaction and ab initio in-medium similarity renormalization group calculations with chiral effective field theory nucleon-nucleon and three-nucleon forces.

• Benito, J.; Lenzi, S.M.; Recchia, F.; Axiotis, M.; Aydin, Selda & Bazzacco, D. [Vis alle 45 forfattere av denne artikkelen] (2024). Spectroscopy of Neutron-rich Fe Isotopes Populated in the 70Zn + 238U Reaction. Acta Physica Polonica B, Proceedings Supplement. ISSN 1899-2358. 17(3). doi: 10.5506/APhysPolBSupp.17.3-A4. Fulltekst i vitenarkiv Vis sammendrag

  The excited states of neutron-rich Fe isotopes have been studied through a multinucleon transfer reaction of a 70Zn beam on a 238U target. Unambiguous identification of prompt γ rays belonging to each nucleus was performed by coincidence detection of the ions in a high-acceptance magnetic spectrometer. The observed spectra are compared with large-scale shell-model calculations in the fpgd model space.

• Li, P.J.; Lee, J.; Doornenbal, P.; Chen, S.; Wang, S. & Obertelli, A. [Vis alle 49 forfattere av denne artikkelen] (2024). Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes. Physics Letters B. ISSN 0370-2693. 855. doi: 10.1016/j.physletb.2024.138828. Fulltekst i vitenarkiv
• Zidarova, R.; Cortés, M.L.; Werner, V.; Koseoglou, P.; Pietralla, N. & Doornenba, P. [Vis alle 78 forfattere av denne artikkelen] (2024). Gamma-ray spectroscopy of 55Sc. Physica Scripta. ISSN 0031-8949. 99(7). doi: 10.1088/1402-4896/ad5594. Fulltekst i vitenarkiv Vis sammendrag

  The N = 34 isotope 55Sc has been investigated using in-beam γ-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. Spectra from the direct (p, pn) reaction as well as indirect reaction channels have been investigated. γ rays with energies 496(10), 570(12), 682(14), 1510(30), 1780(36), 2345(57) and 2470(50) keV have been observed. A level scheme was constructed based on γγ coincidence analysis and relative intensities. The results have been compared to the level scheme already reported in literature, as well as to large-scale shell model calculations in the sd − pf model space. A new level at 1510keV, decaying directly to the ground state, has been proposed and spin-parity Jπ = 7/2− was tentatively assigned. The effect of including the νg9/2 orbital is discussed. It can be concluded that the main low-energy properties of 55Sc seem to be included in the original sd − pf model space.

• Linh, B.D.; Corsi, A.; Gillibert, A.; Obertelli, A.; Doornenbal, P. & Barbieri, C. [Vis alle 88 forfattere av denne artikkelen] (2024). Onset of collectivity for argon isotopes close to N=32. Physical Review C. ISSN 2469-9985. 109(3). doi: 10.1103/PhysRevC.109.034312. Fulltekst i vitenarkiv
• Markova, Maria; Larsen, Ann-Cecilie; Tveten, Gry Merete; Neumann-Cosel, Peter von; Eriksen, Tomas Kvalheim & Garrote, Frank Leonel Bello [Vis alle 16 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Chen, S.; Browne, F.; Doornenbal, P.; Lee, J.; Obertelli, A. & Tsunoda, Y. [Vis alle 83 forfattere av denne artikkelen] (2023). Level structures of ^56,58Ca cast doubt on a doubly magic ⁶⁰Ca. Physics Letters B. ISSN 0370-2693. 843. doi: 10.1016/j.physletb.2023.138025. Fulltekst i vitenarkiv
• Larsen, Ann-Cecilie; Tveten, Gry Merete; Renstrøm, Therese; Utsunomiya, H.; Algin, E. & Ari-Izumi, T. [Vis alle 31 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv
• Pasqualato, G; Ansari, S.; Heines, Johannes Sørby; Modamio, Victor; Görgen, Andreas & Beckmann, Kristine Sønstevold [Vis alle 52 forfattere av denne artikkelen] (2023). Shape evolution in even-mass ^{98 - 104} Zr isotopes via lifetime measurements using the γγ -coincidence technique. European Physical Journal A. ISSN 1434-6001. 59(11). doi: 10.1140/epja/s10050-023-01172-8. Fulltekst i vitenarkiv Vis sammendrag

  The Zirconium (Z = 40) isotopic chain has attracted interest for more than four decades. The abrupt lowering of the energy of the first 2+ state and the increase in the transition strength B(E2; 2+→ 0+) going from 98Zr to 100Zr has been the first example of “quantum phase transition” in nuclear shapes, which has few equivalents in the nuclear chart. Although a multitude of experiments have been performed to measure nuclear properties related to nuclear shapes and collectivity in the region, none of the measured lifetimes were obtained using the Recoil Distance Doppler Shift method in the γγ-coincidence mode where a gate on the direct feeding transition of the state of interest allows a strict control of systematical errors. This work reports the results of lifetime measurements for the first yrast excited states in 98−104Zr carried out to extract reduced transition probabilities. The new lifetime values in γγ-coincidence and γ -single mode are compared with the results of former experiments. Recent predictions of the Interacting Boson Model with Configuration Mixing, the Symmetry Conserving Configuration Mixing model based on theHartree–Fock–Bogoliubov approach and the Monte Carlo Shell Model are presented and compared with the experimental data.

• Pedersen, Line Gaard; Sahin, Eda; Görgen, Andreas; Garrote, Frank Leonel Bello; Tsunoda, Y. & Otsuka, T. [Vis alle 67 forfattere av denne artikkelen] (2023). First spectroscopic study of odd-odd Cu 78. Physical Review C. ISSN 2469-9985. 107(4). doi: 10.1103/PhysRevC.107.044301. Fulltekst i vitenarkiv Vis sammendrag

  Nuclei in the vicinity of 78Ni are important benchmarks for nuclear structure, which can reveal changes in the shell structure far from stability. Spectroscopy of the odd-odd isotope 78Cu was performed for the first time in an experiment with the EURICA setup at the Radioactive Isotope Beam Factory at RIKEN Nishina Center. Excited states in the neutron-rich isotope were populated following the β decay of 78Ni produced by in-flight fission and separated by the BigRIPS separator. A level scheme based on the analysis of γ−γ coincidences is presented. Tentative spin and parity assignments were made when possible based on the β-decay feeding intensities and γ-decay properties of the excited states. Time correlations between β and γ decay show clear indications of an isomeric state with a half-life of 3.8(4) ms. Large-scale Monte Carlo shell-model calculations were performed using the A3DA-m interaction and a valence space comprising the full fp shell and the 1g9/2 and 2d5/2 orbitals for both protons and neutrons. The comparison of the experimental results with the shell-model calculations allows interpreting the excited states in terms of spin multiplets arising from the proton-neutron interaction. The results provide further insight into the evolution of the proton single-particle orbitals as a function of neutron number, and quantitative information about the proton-neutron interaction outside the doubly magic 78Ni core.

• Galtarossa, F.; Scomparin, L.; Angelis, Giacomo de; Marchi, T.; Baumann, T. & Bazin, D. [Vis alle 24 forfattere av denne artikkelen] (2023). Proton inelastic scattering on 68,70,72Ni. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. doi: 10.1088/1742-6596/2586/1/012086. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The proton inelastic scattering on 68,70,72 Ni isotopes was measured at the NSCL at MSU, employing the S800 spectrometer coupled to the GRETINA γ-ray array. The aim of the experiment was to determine the degree of collectivity in these neutron-rich Z = 28 isotopes. The use of a hadronic probe allows to complement previous Coulomb excitation measurements of the reduced transition probability B(E2; 0 + → 2 + ) and deduce the neutron-to-proton transition matrix elements ratio. The high resolution in γ-ray energy achievable with GRETINA gives large control on feeding transitions, thus reducing possible systematics errors in the determination of transition strengths.

• Pedersen, Line Gaard; Sahin, Eda; Görgen, Andreas; Garrote, Frank Leonel Bello; Tsunoda, Yusuke & Otsuka, Takaharu [Vis alle 67 forfattere av denne artikkelen] (2023). Experimental Level Scheme of 78Cu. Acta Physica Polonica B. ISSN 0587-4254. 16. doi: 10.5506/APhysPolBSupp.16.4-A14. Fulltekst i vitenarkiv
• Pogliano, Francesco; Garrote, Frank Leonel Bello; Larsen, Ann-Cecilie; Berg, Hannah Christine; Gjestvang, Dorthea & Görgen, Andreas [Vis alle 19 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Enciu, M.; Liu, H.N.; Obertelli, A.; Doornenbal, P.; Nowacki, F. & Ogata, K. [Vis alle 78 forfattere av denne artikkelen] (2022). Extended p3/2 Neutron Orbital and the N=32 Shell Closure in Ca 52. Physical Review Letters. ISSN 0031-9007. 129(26). doi: 10.1103/PhysRevLett.129.262501. Fulltekst i vitenarkiv Vis sammendrag

  The one-neutron knockout from 52Ca in inverse kinematics onto a proton target was performed at ∼230  MeV/nucleon combined with prompt γ spectroscopy. Exclusive quasifree scattering cross sections to bound states in 51Ca and the momentum distributions corresponding to the removal of 1f7/2 and 2p3/2 neutrons were measured. The cross sections, interpreted within the distorted-wave impulse approximation reaction framework, are consistent with a shell closure at the neutron number N=32, found as strong as at N=28 and N=34 in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 1f7/2 and 2p3/2 orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the 2p3/2 orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.

• Elekes, Z.; Juhász, M.M.; Sohler, D.; Sieja, K.; Yoshida, K. & Ogata, K. [Vis alle 79 forfattere av denne artikkelen] (2022). "southwestern" boundary of the N=40 island of inversion: First study of low-lying bound excited states in v 59 and v 61. Physical Review C. ISSN 2469-9985. 106(6). doi: 10.1103/PhysRevC.106.064321. Fulltekst i vitenarkiv Vis sammendrag

  The low-lying level structure of 59V and 61V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for 61V while the neutron knock-out reaction provided the data for 59V. Four and five new transitions were determined for 59V and 61V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed γ rays for each isotope could be placed in the level scheme and assigned to the decay of the first 11/2− and 9/2− levels. The (p,p′) excitation cross sections for 61V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, 61V could not be unambiguously placed on the island of inversion.

• Guttormsen, Magne Sveen; Ay, Kursad Osman; Ozgur, Mustafa; Algin, Emel; Larsen, Ann-Cecilie & Garrote, Frank Leonel Bello [Vis alle 26 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Grocutt, L.; Chapman, R.; Bouhelal, M.; Haas, F.; Goasduff, A. & Smith, J.F. [Vis alle 35 forfattere av denne artikkelen] (2022). Lifetime measurements of states of S 35, S 36, S 37, and S 38 using the AGATA γ -ray tracking spectrometer. Physical Review C. ISSN 2469-9985. 106(2). doi: 10.1103/PhysRevC.106.024314. Fulltekst i vitenarkiv Vis sammendrag

  Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A=35, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of 36S ions of energy 225 MeV incident on a thin 208Pb target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ-ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For 35S, the lifetime was determined for the first 1/2+ state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the 3− state of 36S at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6+) state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For 37S, the states for which lifetime limits were established were those at 646 keV with Jπ=3/2− and at 2776 keV with Jπ=11/2−; there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the Jπ=(6+) state of 38S at 3675 keV; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

• Markova, Maria; Larsen, Ann-Cecilie; Neumann-Cosel, Peter von; Bassauer, Sergej; Görgen, Andreas & Guttormsen, Magne Sveen [Vis alle 23 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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).

• Koiwai, T.; Wimmer, K.; Doornenbal, P.; Obertelli, A.; Barbieri, C. & Duguet, T. [Vis alle 83 forfattere av denne artikkelen] (2022). A first glimpse at the shell structure beyond ⁵⁴Ca: Spectroscopy of ⁵⁵K, ⁵⁵Ca, and ⁵⁷Ca. Physics Letters B. ISSN 0370-2693. 827. doi: 10.1016/j.physletb.2022.136953. Fulltekst i vitenarkiv
• Guttormsen, Magne Sveen; Alhassid, Yoram; Ryssens, Wouter; Ay, K.o.; Ozgur, Mustafa & Algin, Emel [Vis alle 22 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Yokoyama, R.; Ideguchi, E.; Simpson, G.S.; Tanaka, Mn.; Sun, Yang & Lv, Cui-Juan [Vis alle 55 forfattere av denne artikkelen] (2021). Three-quasiparticle isomers in odd-even Pm 159,161: Calling for modified spin-orbit interaction for the neutron-rich region. Physical Review C. ISSN 2469-9985. 104(2). doi: 10.1103/PhysRevC.104.L021303. Fulltekst i vitenarkiv Vis sammendrag

  Neutron-rich Pm (Z=61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, RIKEN Nishina Center using the in-flight fission of a 345 MeV/nucleon 238U beam. A cluster-type Ge detector array, EURICA, was used to measure the delayed γ rays from stopped ions. Isomeric γ decays were observed in 159Pm and 161Pm with half-lives of 4.97(12) μs and 0.79(4) μs, respectively. Level schemes for 159Pm and 161Pm were constructed in this study. The isomeric states of 159Pm and 161Pm could be interpreted as two quasiparticle excitations of neutrons with the configurations of ν(7/2[633]⊗5/2[523]) and ν(7/2[633]⊗1/2[521]), respectively. They are analogous to the isomers that have been observed systematically in other even-mass N=98 and N=100 isotones in this region. A projected shell model calculation was performed and it reproduced the order of three-quasiparticle states only if new Nilsson parameters with an N-dependent spin-orbit interaction were used. This work demonstrates that the strength of spin-orbit interactions in standard Nilsson parameters needs to be modified to study the properties of neutron-rich rare-earth nuclei around A=165, and provides new evidence supporting the existence of the deformed N=98 subshell gap in odd-mass nuclei for the first time.

• Linh, B.D.; Corsi, A.; Gillibert, A.; Obertelli, A.; Doornenbal, P. & Barbieri, C. [Vis alle 86 forfattere av denne artikkelen] (2021). Investigation of the ground-state spin inversion in the neutron-rich isotopes. Physical Review C. ISSN 2469-9985. 104(4). doi: 10.1103/PhysRevC.104.044331. Fulltekst i vitenarkiv
• Juhász, M.M.; Elekes, Z.; Sohler, D.; Utsuno, Y.; Yoshida, K. & Otsuka, Takahuro [Vis alle 80 forfattere av denne artikkelen] (2021). First spectroscopic study of ⁵¹Ar by the (p,2p) reaction. Physics Letters B. ISSN 0370-2693. 814. doi: 10.1016/j.physletb.2021.136108. Fulltekst i vitenarkiv Vis sammendrag

  The nuclear structure of 51Ar, an uncharted territory so far, was studied by the (p,2p) reaction using γ-ray spectroscopy for the bound states and the invariant mass method for the unbound states. Two peaks were detected in the γ-ray spectrum and six peaks were observed in the 50Ar+n relative energy spectrum. Comparing the results to our shell-model calculations, two bound and six unbound states were established. Three of the unbound states could only be placed tentatively due to the low number of counts in the relative energy spectrum of events associated with the decay through the first excited state of 50Ar. The low cross sections populating the two bound states of 51Ar could be interpreted as a clear signature for the presence of significant subshell closures at neutron numbers 32 and 34 in argon isotopes. It was also revealed that due to the two valence holes, unbound collective states coexist with individual-particle states in 51Ar.

• Browne, F.; Chen, S.; Doornenbal, P.; Obertelli, A.; Ogata, K. & Utsuno, Y. [Vis alle 85 forfattere av denne artikkelen] (2021). Pairing Forces Govern Population of Doubly Magic Ca 54 from Direct Reactions. Physical Review Letters. ISSN 0031-9007. 126(25). doi: 10.1103/PhysRevLett.126.252501. Fulltekst i vitenarkiv
• Escrig, S.; Morales, A.I.; Nishimura, S.; Niikura, M.; Poves, A & Xu, Z.Y. [Vis alle 43 forfattere av denne artikkelen] (2021). Persistence of the Z=28 shell gap in A=75 isobars: Identification of a possible (1/2-) μ s isomer in Co 75 and β decay to Ni 75. Physical Review C. ISSN 2469-9985. 103(6). doi: 10.1103/PhysRevC.103.064328. Fulltekst i vitenarkiv
• Markova, Maria; Neumann-Cosel, Neumann-Cosel von; Larsen, A.C.; Bassauer, S.; Görgen, A. & Guttormsen, Magne Sveen [Vis alle 25 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Scomparin, L.; Marchi, T.; Angelis, G. De; Baumann, T.; Bazin, D. & Gade, A. [Vis alle 24 forfattere av denne artikkelen] (2021). Proton inelastic scattering in ^68,70,72Ni isotopes. Nuovo cimento della societa italiana de fisica. C, Geophysics and space physics. ISSN 1124-1896. 44(2-3). doi: 10.1393/ncc/i2021-21077-6. Fulltekst i vitenarkiv Vis sammendrag

  A preliminary analysis of the proton inelastic scattering of 68,70,72Ni at intermediate energies will be discussed. This measurement is important for the study of the nuclear shell’s evolution in the nickel isotopic chain. A brief description of the physics case, the setup, and the particle identification methods will be presented.

• Juhász, M.M.; Elekes, Z.; Sohler, D.; Sieja, K.; Yoshida, K. & Ogata, K. [Vis alle 79 forfattere av denne artikkelen] (2021). First spectroscopic study of v 63 at the N=40 island of inversion. Physical Review C. ISSN 2469-9985. 103(6), s. 1–10. doi: 10.1103/PhysRevC.103.064308. Fulltekst i vitenarkiv Vis sammendrag

  The low-lying level structure of 63V was studied for the first time by the inelastic proton scattering and the proton knock-out reaction in inverse kinematics. The comparison of the newly observed γ-ray transitions at 696(8) keV and 889(16) keV with our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja interaction established two excited states proposed to be the first 11/2− and 9/2− levels. The (p,p′) excitation cross sections were analyzed by the coupled channel formalism assuming pure quadrupole as well as quadrupole+hexadecapole deformations. This resulted in large deformation parameters placing 63V in the island of inversion located below 68Ni.

• Wimmer, K.; Korten, W.; Doornenbal, P.; Arici, T.; Aguilera, P. & Algora, A. [Vis alle 38 forfattere av denne artikkelen] (2021). Shape Changes in the Mirror Nuclei Kr 70 and Se 70. Physical Review Letters. ISSN 0031-9007. 126(7). doi: 10.1103/PhysRevLett.126.072501. Fulltekst i vitenarkiv
• Tonev, D; Angelis, G. De; Deloncle, I.; Goutev, N.; Gregorio, Gregorio De & Pavlov, P. [Vis alle 31 forfattere av denne artikkelen] (2021). Transition probabilities in ³¹P and ³¹S: A test for isospin symmetry. Physics Letters B. ISSN 0370-2693. 821. doi: 10.1016/j.physletb.2021.136603. Fulltekst i vitenarkiv
• Wimmer, K.; Arici, T.; Korten, W.; Doornenbal, P.; Delaroche, J.-P. & Girod, M. [Vis alle 44 forfattere av denne artikkelen] (2020). Shape coexistence revealed in the N=Zisotope72Kr through inelastic scattering. European Physical Journal A. ISSN 1434-6001. 56(6). doi: 10.1140/epja/s10050-020-00171-3. Fulltekst i vitenarkiv
• Sun, Y. L.; Obertelli, A.; Doornenbal, P.; Barbieri, C.; Chazono, Y. & Duguet, T. [Vis alle 84 forfattere av denne artikkelen] (2020). Restoration of the natural E(1/2) - E(3/2) energy splitting in odd-K isotopes towards N = 40. Physics Letters B. ISSN 0370-2693. 802, s. 1–7. doi: 10.1016/j.physletb.2020.135215. Fulltekst i vitenarkiv
• Lokotko, T.; Leblond, S.; Lee, J.; Doornenbal, P.; Obertelli, A. & Poves, A. [Vis alle 67 forfattere av denne artikkelen] (2020). Shell structure of the neutron-rich isotopes Co 69,71,73. Physical Review C. ISSN 2469-9985. 101(3). doi: 10.1103/PhysRevC.101.034314. Fulltekst i vitenarkiv
• Frotscher, A; Gomez-Ramos, M; Obertelli, A; Doornenbal, P; Authelet, G & Baba, H [Vis alle 50 forfattere av denne artikkelen] (2020). Sequential Nature of (p,3p) Two-Proton Knockout from Neutron-Rich Nuclei. Physical Review Letters. ISSN 0031-9007. 125(1). doi: 10.1103/PhysRevLett.125.012501. Fulltekst i vitenarkiv
• Kibédi, T.; Alshahrani, B.; Stuchbery, A.E.; Larsen, Ann-Cecilie; Görgen, Andreas & Siem, Sunniva [Vis alle 20 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Koseoglou, P.; Werner, V.; Pietralla, N.; Söderström, P.-A.; Doornenbal, P. & Obertelli, A. [Vis alle 75 forfattere av denne artikkelen] (2020). Spectroscopy of neutron-rich scandium isotopes. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 1555(1). doi: 10.1088/1742-6596/1555/1/012026. Fulltekst i vitenarkiv Vis sammendrag

  Within the SEASTAR III campaign at the Radioactive Isotope Beam Factory, at the RIKEN Nishina Center, neutron-rich isotopes in the vicinity of 53K were produced from the fragmentation of the primary 70Zn beam on a 9Be target. After nucleon knockout reactions on the secondary liquid hydrogen MINOS target the known γ rays of the neutron-rich 55Sc isotope were observed (shown in this proceedings) and γ rays from 57,59Sc isotopes have been identified for the first time. The evolution of the occupied nucleon orbitals of these nuclei in the ground and excited state is investigated under the prism of the tensor force.

• Garrote, Frank Leonel Bello; Sahin, Eda; Tsunoda, Y.; Otsuka, T.; Görgen, Andreas & Niikura, M. [Vis alle 67 forfattere av denne artikkelen] (2020). β decay of Ni 75 and the systematics of the low-lying level structure of neutron-rich odd-A Cu isotopes. Physical Review C. ISSN 2469-9985. 102(3). doi: 10.1103/PhysRevC.102.034314. Fulltekst i vitenarkiv Vis sammendrag

  Background: Detailed spectroscopy of neutron-rich odd-A Cu isotopes is of great importance for studying the shell evolution in the region of 78Ni. While there is experimental information on excited states in 69−73,77,79Cu isotopes, the information concerning 75Cu is very limited. Purpose: Experimentally observed single-particle, core-coupling, and proton-hole intruder states in 75Cu, will complete the systematics of these states in the chain of isotopes. Method: Excited states in 75Cu were populated in the β decay of 75Ni isotopes. The Ni nuclei were produced by the in-flight fission of 238U projectiles, and were separated, identified, and implanted in a highly segmented Si detector array for the detection of the β-decay electrons. The β-delayed γ rays were detected in a HPGe cluster array. Monte Carlo shell model calculations were performed using the A3DA interaction built on the pfg9/2d5/2 model space for both neutrons and protons. Results: A level scheme of 75Cu was built up to ≈4 MeV by performing a γ−γ coincidence analysis. The excited states below 2 MeV were interpreted based on the systematics of neutron-rich odd-A Cu isotopes and the results of the shell model calculations. Conclusions: The evolution of the single-particle, core-coupling, and proton-hole intruder states in the chain of neutron-rich odd-A Cu isotopes is discussed in the present work, in connection with the newly observed level structure of 75Cu.

• Cortés, M.L.; Rodriguez, W.; Doornenbal, P.; Obertelli, A.; Holt, J.D. & Menéndez, J. [Vis alle 81 forfattere av denne artikkelen] (2020). N=32 shell closure below calcium: Low-lying structure of Ar 50. Physical Review C. ISSN 2469-9985. 102(6). doi: 10.1103/PhysRevC.102.064320. Fulltekst i vitenarkiv
• Cortés, Martha Liliana; Rodriguez, W.; Doornenbal, P.; Obertelli, A.; Holt, J. D. & Lenzi, S. [Vis alle 84 forfattere av denne artikkelen] (2020). Shell evolution of N = 40 isotones towards 60Ca: First spectroscopy of 62Ti. Physics Letters B. ISSN 0370-2693. 800:135071, s. 1–7. doi: 10.1016/j.physletb.2019.135071. Fulltekst i vitenarkiv
• Wrzosek-Lipska, K; Prochniak, L.; Garrett, P.E.; Yates, S. W.; Wood, J.L. & Napiorkowski, P.J. [Vis alle 36 forfattere av denne artikkelen] (2020). Quadrupole Deformation of 110Cd Studied with Coulomb Excitation. Acta Physica Polonica B. ISSN 0587-4254. 51. doi: 10.5506/APhysPolB.51.789. Fulltekst i vitenarkiv Vis sammendrag

  The low-energy electromagnetic structure of 110Cd was studied using safe-energy Coulomb excitation at the Heavy Ion Laboratory, University of Warsaw. The preliminary results on the quadrupole deformation of lowlying 0+ states in 110Cd are presented and compared to the recent beyondmean- field and General Bohr Hamiltonian calculations.

• Gottardo, A.; Angelis, G. De; Doornenbal, P.; Coraggio, L.; Gargano, A. & Itaco, N. [Vis alle 59 forfattere av denne artikkelen] (2020). Transition strengths in the neutron-rich 73,74,75Ni isotopes. Physical Review C. ISSN 2469-9985. 102. doi: 10.1103/PhysRevC.102.014323. Fulltekst i vitenarkiv Vis sammendrag

  Reduced transition probabilities have been measured for the neutron-rich 73,74,75Ni nuclei with relativistic Coulomb excitation performed at the RIKEN Nishina Center. For the even-even Ni isotope the determined B(E2;0+→2+) value is compatible within errors with the result of a previous intermediate energy Coulomb excitation experiment, although being somewhat larger. For the odd Ni isotopes B(E2) values have been determined for the first time. In the middle νg9/2 shell nucleus 73Ni three peak candidates have been observed and tentatively assigned to the (5/2+), (13/2+), and (11/2+) excitations. Two peak candidates have been observed in 75Ni and tentatively assigned to the (13/2+) and (11/2+) levels. The measured B(E2) values are in line with the large B(E2) reported in 70Ni and at variance with the small strength measured in 72Ni. Excitation energies compare well with the result of large-scale shell-model calculations, while B(E2) values are larger than predicted. This could indicate an increasing contribution of proton excitations across the Z=28 shell closure when approaching 78Ni.

• Ingeberg, Vetle Wegner; Siem, Sunniva; Wiedeking, Mathis; Sieja, Kamila; Bleuel, D.l. & Brits, C.P. [Vis alle 29 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Wimmer, Kathrin; Doornenbal, P; Korten, W; Aguilera, P; Algora, A & Ando, T [Vis alle 34 forfattere av denne artikkelen] (2019). Discovery of 68Br in secondary reactions of radioactive beams. Physics Letters B. ISSN 0370-2693. 795, s. 266–270. doi: 10.1016/j.physletb.2019.06.014. Fulltekst i vitenarkiv Vis sammendrag

  The proton-rich isotope 68Br was discovered in secondary fragmentation reactions of fast radioactive beams. Proton-rich secondary beams of 70,71,72Kr and 70Br, produced at the RIKEN Nishina Center and identified by the BigRIPS fragment separator, impinged on a secondary 9Be target. Unambiguous particle identification behind the secondary target was achieved with the ZeroDegree spectrometer. Based on the expected direct production cross sections from neighboring isotopes, the lifetime of the ground or long-lived isomeric state of 68Br was estimated. The results suggest that secondary fragmentation reactions, where relatively few nucleons are removed from the projectile, offer an alternative way to search for new isotopes, as these reactions populate preferentially low-lying states.

• Taniuchi, R; Santamaria, C; Doornenbal, P.; Obertelli, A.; Yoneda, K. & Authelet, G. [Vis alle 71 forfattere av denne artikkelen] (2019). 78Ni revealed as a doubly magic stronghold against nuclear deformation. Nature. ISSN 0028-0836. 569, s. 53–58. doi: 10.1038/s41586-019-1155-x. Fulltekst i vitenarkiv
• Matejska-Minda, M; Bednarczyk, P; Fornal, B; Xu, F.R.; Liang, W. Y. & Angelis, G De [Vis alle 27 forfattere av denne artikkelen] (2019). Lifetime measurements of short-lived excited states, and shape changes in 69As and 66Ge nuclei. Physical Review C. ISSN 2469-9985. 100(5). doi: 10.1103/PhysRevC.100.054330. Fulltekst i vitenarkiv Vis sammendrag

  Background: The nuclear shape is a macroscopic feature of an atomic nucleus that is sensitive to the underlying nuclear structure in terms of collectivity and the interaction between nucleons. Therefore, the evolution of nuclear shapes has attracted many theoretical and experimental nuclear structure studies. The structure of the A≈ 70 , N≈ Z nuclei, lying far from the stability line, is interesting because a particularly strong proton-neutron correlation may occur here due to the occupation of the same orbits by nucleons of both types. In this region, different particle configurations drive a nucleus towards various deformed shapes: prolate, oblate, octupole, or nonaxial. These nuclear shapes change rapidly with nucleon number and also with angular momentum. This is reflected by a presence of different structures (bands) of excited states which exhibit a broad range of lifetimes. Purpose: The aim of this paper is to determine lifetimes of some high-spin excited states in 69 As and 66 Ge nuclei to examine the shape evolution in these neutron-deficient nuclei. Methods: Lifetimes of high-spin states in 69 As and 66 Ge have been measured by using the Doppler-shift attenuation technique with the GASP and recoil filter detector setup at the Laboratori Nazionali di Legnaro. The nuclei of interest were produced in the 32 S ( 95 MeV ) + 0.8 mg / cm 2 40 Ca fusion-evaporation reaction. The strongest reaction channels 3p and α 2 p led to the 69 As and 66 Ge final nuclei, respectively. Using γ − γ -recoil coincidences we were able to determine very short lifetimes (in the femtosecond range) in the residual nuclei of interest. Results: In 69 As , the extracted lifetimes are τ = 72 ( − 32 , +45 ) fs for the 33 / 2 + state at 7897 keV and τ < 85 fs for the 37 / 2 + state at 9820 keV. For the 66 Ge case, the lifetime of the 11 − state at 7130 keV is τ = 122 ( ± 41 ) fs. Lifetimes in 69 As and 66 Ge reported in this paper have been measured for the first time in the present experiment. Conclusions: The results are discussed in the terms of deformation and shape evolution in 69 As and 66 Ge . The quadrupole moments deduced from the measured lifetimes were compared with the cranked Woods-Saxon-Strutinsky calculations by means of the total Routhian surface method. It turns out that Band 3 in 69 As shows an oblate-prolate shape transition, and above spin 33 / 2 + it corresponds to a prolate collective structure with β 2 ≈ 0.27 and γ ≈ 20 ∘ . In turn, in 66 Ge the negative-parity band built on the 7− state at 4205 keV corresponds to a triaxial shape with β 2 = 0.33 and γ = 31 ∘ . Analysis of the transitional quadrupole moments derived from the experimental and theoretical ones points to a significant change of deformation in the 69 As and 66 Ge nuclei with increasing rotational frequency.

• Vaquero, V; Jungclaus, Andrea; Rodriguez-Sanchez, J. L.; Tostevin, J. A.; Doornenbal, P. & Wimmer, K [Vis alle 34 forfattere av denne artikkelen] (2019). Inclusive cross sections for one- and multi-nucleon removal from Sn, Sb, and Te projectiles beyond the N = 82 shell closure. Physics Letters B. ISSN 0370-2693. 795, s. 356–361. doi: 10.1016/j.physletb.2019.06.035. Fulltekst i vitenarkiv Vis sammendrag

  Inclusive one- and multi-nucleon removal cross sections have been measured for several Sn, Sb and Te isotopes just beyond the neutron shell closure. The beams were produced in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. The experimental cross sections are compared to predictions from the most recent version of the Liege intranuclear cascade model. Although the overall agreement is good, severe discrepancies are observed for the cases of one- and two-neutron removal from 134Sn and 135Sb projectiles and one-proton knockout from all measured isotones. These discrepancies, as well as the relevance of quasi-elastic reaction channels to the one-neutron removal cross sections, are discussed. In addition, the measured inclusive one-proton knockout cross section for the semi-magic 134Sn projectile is compared to eikonal direct reaction theory calculations to assess if the suppression factors to these calculated cross sections, deduced from data on reactions of lighter projectile nuclei, are also applicable to heavy nuclei.

• Chen, S.; Lee, J; Doornenbal, P; Obertelli, A; Barbieri, C & Chazono, Y [Vis alle 83 forfattere av denne artikkelen] (2019). Quasifree neutron knockout from 54Ca corroborates arising N=34 neutron magic number. Physical Review Letters. ISSN 0031-9007. 123(14), s. 1–7. doi: 10.1103/PhysRevLett.123.142501. Fulltekst i vitenarkiv
• Elekes, Z; Kripkó, Á; Sohler, D; Sieja, K; Ogata, K. & Yoshida, K [Vis alle 67 forfattere av denne artikkelen] (2019). Nuclear structure of 76Ni from the (p,2p) reaction. Physical Review C. ISSN 2469-9985. 99:014312(1), s. 1–7. doi: 10.1103/PhysRevC.99.014312. Fulltekst i vitenarkiv Vis sammendrag

  The nuclear structure of the 76 Ni nucleus was investigated by ( p , 2 p ) reaction using a NaI(Tl) array to detect the deexciting prompt γ rays. A new transition with an energy of 2227 keV was identified by γ γ and γ γ γ coincidences. According to these coincidence spectra the observed transition connects a new state at 4147 keV and the previously known 4+1 state at 1920 keV. Two weaker transitions were also obtained at 2441 and 2838 keV, which could be tentatively placed to feed the known 2+1 state at 990 keV. Our shell-model calculations using the Lenzi, Nowacki, Poves, and Sieja interaction produced good candidates for the experimental proton hole states in the observed energy region, and the theoretical cross sections showed good agreement with the experimental values. Although we could not assign all the experimental states to the theoretical ones unambiguously, the results are consistent with a reasonably large Z=28 shell gap for nickel isotopes in accordance with previous studies.

• Grocutt, L; Chapman, R; Bouhelal, M; Haas, F; Goasduff, A & Smith, J. F. [Vis alle 34 forfattere av denne artikkelen] (2019). Lifetime measurements of N≃20 phosphorus isotopes using the AGATA γ-ray tracking spectrometer. Physical Review C. ISSN 2469-9985. 100(6). doi: 10.1103/PhysRevC.100.064308. Fulltekst i vitenarkiv Vis sammendrag

  Lifetimes of excited states of the phosphorus isotopes 33 , 34 , 35 , 36 15 P have been measured by using the differential recoil-distance method. The isotopes of phosphorus were populated in binary grazing reactions initiated by a beam of 36 S ions of energy 225 MeV incident on a thin 208 Pb target mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ -ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were made within the range from about 1 to 100 ps. The number of states for which lifetime measurements were possible was limited by statistics. For 33 P , lifetime limits were determined for the first 3/2+ and 5/2+ states at 1431 and 1848 keV, respectively; the results are compared with previous published lifetime values. The lifetime of the first 2+ state of 34 P at 429 keV was determined and compared with earlier measurements. For 35 P , the states for which lifetimes, or lifetime limits, were determined were those at 2386, 3860, 4101, and 4493 keV, with Jπ values of 3/2+, 5/2+, 7/2− 1 , and 7/2− 2 , respectively. There have been no previous published lifetimes for states in this nucleus. A lifetime was measured for the stretched π ( 1 f 7 / 2 ) ⊗ ν ( 1 f 7 / 2 ) J π = ( 7 + ) state of 36 P at 5212 keV and a lifetime limit was established for the stretched π ( 1 d 3 / 2 ) ⊗ ν ( 1 f 7 / 2 ) J π = ( 5 − ) state at 2030 keV. There are no previously published lifetimes for states of 36 P . Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF effective interaction. In addition, measured branching ratios, published mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. In general, there is good agreement between experiment and the shell model; however there is evidence that the shell-model values of the M1 transition rates for the 3/2+1→ 1 / 2 + (ground state) and 5/2+1→ 3 / 2 + 1 transitions in 33 P underestimate the experimental values by a factor between 5 and 10. In 35 P there are some disagreements between experimental and shell-model values of branching ratios for the first and second excited 7/2− states. In particular, there is a serious disagreement for the decay characteristics of the second 7/2− state at 4493 keV, for which the shell-model counterpart lies at 4754 keV. In this case, the shell-model competing electromagnetic decay branches are dominated by E1 and M1 transitions.

• Liu, H.N.; Obertelli, A; Doornenbal, P; Bertulani, C. A.; Hagen, G & Holt, J. D. [Vis alle 80 forfattere av denne artikkelen] (2019). How Robust is the N=34 Subshell Closure? First Spectroscopy of 52Ar. Physical Review Letters. ISSN 0031-9007. 122(7). doi: 10.1103/PhysRevLett.122.072502. Fulltekst i vitenarkiv
• Sahin, Eda; Hadynska-Klek, Katarzyna; Garrote, Frank Leonel Bello & Görgen, Andreas (2019). Probing the nuclear structure in the vicinity of 78Ni. The European Physical Journal Conferences. ISSN 2101-6275. 223. doi: 10.1051/epjconf/201922301054. Fulltekst i vitenarkiv Vis sammendrag

  Theoretical and experimental studies of neutron-rich nuclei have shown that the general concept of shell structure is not as robust and universal as earlier thought, but can exhibit significant changes as a function of neutron excess. New magic numbers appear and some other conventional ones disappear mainly because of a different ordering of the single-particle orbitals. In the present contribution, recent experimental studies of neutron-rich Cu isotopes, performed at RIKEN using β decay and one-proton knockout reactions, will be discussed. Neutron-rich nuclei near 78Ni were populated through in-flight fission of 238U on thick 9Be targets in both experiments. In the β-decay study, 75,77Ni nuclei were implanted into the WAS3ABi silicon array, while γ rays from excited states in 75,77Cu emitted after β decay of the implanted ions were detected with the EURICA Ge detector array that was surrounding the active stopper. In a second experiment within the SEASTAR campaign at RIKEN, the same 75,77Cu nuclei were produced in (p,2p) knockout reactions from 76,78Zn beam particles at around 250 MeV/nucleon impinging onto the MINOS liquid hydrogen target. In the latter experiment the DALI2 NaI array was used to detect de-excitation γ rays measured in coincidence with Cu nuclei identified in the Zero Degree Spectrometer. Both studies are complimentary and greatly contribute to our understanding on the nuclear structure in the 78Ni region.

• Torres, Diego A.; Chapman, R; Kumar, V; Hadinia, B; Hodsdon, A & Labiche, M [Vis alle 49 forfattere av denne artikkelen] (2019). Study of medium-spin states of neutron-rich 87, 89, 91Rb isotopes. European Physical Journal A. ISSN 1434-6001. 55(9), s. 1–21. doi: 10.1140/epja/i2019-12839-6. Fulltekst i vitenarkiv
• Kullmann, Ina Kristine Berentsen; Larsen, Ann-Cecilie; Renstrøm, Therese; Beckmann, Kristine Sønstevold; Garrote, Frank Leonel Bello & Campo, Lucia Crespo [Vis alle 13 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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. [Vis alle 22 forfattere av denne artikkelen] (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), s. 1–9. doi: 10.1103/PhysRevC.100.024305. Fulltekst i vitenarkiv
• Brits, C.P.; Malatji, Kgashane L.; Wiedeking, M.; Kheswa, BV; Goriely, S. & Garrote, Frank Leonel Bello [Vis alle 27 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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 .

• Kaya, L.; Vogt, A; Reiter, P; Müller-Gatermann, C.; Gargano, A & Coraggio, L [Vis alle 62 forfattere av denne artikkelen] (2019). Identification of high-spin proton configurations in 136Ba and 137Ba. Physical Review C. ISSN 2469-9985. 99(1). doi: 10.1103/PhysRevC.99.014301. Fulltekst i vitenarkiv Vis sammendrag

  The high-spin structures of 136 Ba and 137 Ba are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. 136 Ba is populated in a 136 Xe + 238 U MNT reaction employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and in two 9Be + 130 Te fusion-evaporation reactions using the High-efficiency Observatory for γ -Ray Unique Spectroscopy (HORUS) at the FN tandem accelerator of the University of Cologne, Germany. Furthermore, both isotopes are populated in an elusive reaction channel in the 11 B + 130 Te fusion-evaporation reaction utilizing the HORUS γ -ray array. The level scheme above the Jπ = 10 + isomer in 136 Ba is revised and extended up to an excitation energy of approximately 5.5 MeV. From the results of angular-correlation measurements, the Ex=3707 - and Ex=4920 -keV states are identified as the bandheads of positive- and negative-parity cascades. While the high-spin regimes of both 132 Te and 134 Xe are characterized by high-energy 12 + → 10 + transitions, the 136 Ba E 2 ground-state band is interrupted by negative-parity states only a few hundred keV above the Jπ = 10 + isomer. Furthermore, spins are established for several hitherto unassigned high-spin states in 137 Ba . The new results close a gap along the high-spin structure of N<82 Ba isotopes. Experimental results are compared to large-scale shell-model calculations employing the GCN50:82, Realistic SM, PQM130, and SN100PN interactions. The calculations suggest that the bandheads of the positive-parity bands in both isotopes are predominantly of proton character.

• Liddick, Sean N.; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Spyrou, Artemis; Crider, Benjamin P. & Naqvi, Farheen [Vis alle 30 forfattere av denne artikkelen] (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), s. 1–12. doi: 10.1103/PhysRevC.100.024624. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Paul, N.; Obertelli, A.; Bertulani, C. A.; Corsi, A.; Doornenbal, P. & Rodriguez-Sanchez, J. L. [Vis alle 92 forfattere av denne artikkelen] (2019). Prominence of Pairing in Inclusive (p,2p) and (p,pn) Cross Sections from Neutron-Rich Nuclei. Physical Review Letters. ISSN 0031-9007. 122(16). doi: 10.1103/PhysRevLett.122.162503. Fulltekst i vitenarkiv Vis sammendrag

  Fifty-five inclusive single nucleon-removal cross sections from medium mass neutron-rich nuclei impinging on a hydrogen target at ∼ 250     MeV / nucleon are measured at the RIKEN Radioactive Isotope Beam Factory. Systematically higher cross sections are found for proton removal from nuclei with an even number of protons as compared to odd-proton number projectiles for a given neutron separation energy. Neutron removal cross sections display no even-odd splitting, contrary to nuclear cascade model predictions. Both effects are understood through simple considerations of neutron separation energies and bound state level densities originating in pairing correlations in the daughter nuclei. These conclusions are supported by comparison with semimicroscopic model predictions, highlighting the enhanced role of low-lying level densities in nucleon-removal cross sections from loosely bound nuclei.

• Vaquero, Victor; Jungclaus, Andrea; Doornenbal, Pieter C.; Wimmer, Kathrin; Moro, Antônio M. & Ogata, Kazuyuki [Vis alle 34 forfattere av denne artikkelen] (2019). In-beam γ-ray spectroscopy of 136Te at relativistic energies. Physical Review C. ISSN 2469-9985. 99:034306(3), s. 1–14. doi: 10.1103/PhysRevC.99.034306. Fulltekst i vitenarkiv Vis sammendrag

  The reduced transition probability B(E2;0+1→ 2 + 1 ) to the first excited 2+ state of the neutron-rich nucleus 136 Te , with two protons and two neutrons outside the doubly magic 132 Sn core, was measured via Coulomb excitation at relativistic energies at the RIKEN Radioactive Isotope Beam Factory. A value of B(E2)=0.191 ( 26 ) e2b2 was extracted from the measured inelastic scattering cross section on an Au target taking into account the contributions from both Coulomb and nuclear excitations. In addition, an upper limit for the transition strength to a 2+ state of mixed-symmetry character in the excitation energy range of 1.5–2.2 MeV was determined and compared to the predictions of various theoretical calculations. Because of the high statistics gathered in the present experiment the error of the deduced B(E2) value is dominated by the systematic uncertainties involved in the analysis of Coulomb excitation experiments at beam energies around 150 MeV/u. Therefore, the latter are for the first time assessed in detail in the present work.

• Malatji, Kgashane Leroy; Wiedeking, Mathis; Goriely, Stephane; Brits, Christiaan Petrus; Kheswa, Bonginkosi Vincent & Garrote, Frank Leonel Bello [Vis alle 22 forfattere av denne artikkelen] (2019). Re-estimation of 180Ta nucleosynthesis in light of newly constrained reaction rates. Physics Letters B. ISSN 0370-2693. 791, s. 403–408. doi: 10.1016/j.physletb.2019.03.013. Fulltekst i vitenarkiv
• Kaya, L.; Vogt, A.; Reiter, P; Siciliano, M.; Shimizu, N & Utsuno, Yutaka [Vis alle 71 forfattere av denne artikkelen] (2019). Isomer spectroscopy in 133Ba and high-spin structure of 134Ba. Physical Review C. ISSN 2469-9985. 100(2). doi: 10.1103/PhysRevC.100.024323. Fulltekst i vitenarkiv Vis sammendrag

  The transitional nuclei 134 Ba and 133 Ba are investigated after multinucleon transfer employing the high-resolution Advanced GAmma Tracking Array coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and after fusion-evaporation reaction at the FN tandem accelerator of the University of Cologne, Germany. The Jπ = 19 / 2 + state at 1942 keV in 133 Ba is identified as an isomer with a half-life of 66.6 ( 20 ) ns corresponding to a B(E1) value of 7.7 ( 4 ) × 10 − 6 e 2 fm 2 for the Jπ = 19 / 2 + to Jπ = 19 / 2 − transition. The level scheme of 134 Ba above the Jπ = 10 + isomer is extended to approximately 6 MeV. A pronounced backbending is observed at ℏ ω = 0.38 MeV along the positive-parity yrast band. The results are compared to the high-spin systematics of the Z=56 isotopes. Large-scale shell-model calculations employing the GCN50:82, SN100PN, SNV, PQM130, Realistic SM, and EPQQM interactions reproduce the experimental findings and elucidate the structure of the high-spin states. The shell-model calculations employing the GCN50:82 and PQM130 interactions reproduce alignment properties and provide detailed insight into the microscopic origin of this phenomenon in transitional 134 Ba .

• Hagen, Trine Wiborg; Görgen, Andreas; Korten, Wolfram; Grente, Lucie; Salsac, Marie Delphine & Farget, F. [Vis alle 28 forfattere av denne artikkelen] (2018). Lifetimes of excited states in triaxially deformed 107Tc and 109,111,113Rh. European Physical Journal A. ISSN 1434-6001. 54, s. 1–11. doi: 10.1140/epja/i2018-12482-9. Fulltekst i vitenarkiv
• Litzinger, Julia; Blazhev, Andrey; Dewald, Alfred; Didierjean, Francois; Duchêne, Gaspard G. & Fransen, C. [Vis alle 67 forfattere av denne artikkelen] (2018). Transition probabilities in neutron-rich 80,82Se and the role of the νg9/2 orbital. Physical Review C. ISSN 2469-9985. 97:044323(4), s. 1–13. doi: 10.1103/PhysRevC.97.044323. Fulltekst i vitenarkiv Vis sammendrag

  Transition probabilities of intermediate-spin yrast and non-yrast excitations in 80,82Se were investigated in a recoil distance Doppler-shift (RDDS) experiment performed at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. The Cologne Plunger device for deep inelastic scattering was used for the RDDS technique and was combined with the AGATA Demonstrator array for the γ -ray detection and coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 80Se, the level lifetimes of the yrast (6+ 1 ) and (8+ 1 ) states and of a non-yrast band feeding the yrast 4+ 1 state are determined. A spin and parity assignment of the head of this sideband is discussed based on the experimental results and supported by large-scale shell-model calculations. In 82Se, the level lifetimes of the yrast 6+ 1 state and the yrare 4+ 2 state and lifetime limits of the yrast (10+ 1 ) state and of the 5− 1 state are determined. Although the experimental results contain large uncertainties, they are interpreted with care in terms of large-scale shell-model calculations using the effective interactions JUN45 and jj44b. The excited states’ wave functions are investigated and discussed with respect to the role of the neutron g9/2 orbital.

• Singh, Purnima; Korten, Wolfram; Hagen, Trine Wiborg; Görgen, Andreas; Grente, Lucie & Salsac, Marie Delphine [Vis alle 38 forfattere av denne artikkelen] (2018). Evidence for coexisting shapes through lifetime measurements in 98Zr. Physical Review Letters. ISSN 0031-9007. 121(19). doi: 10.1103/PhysRevLett.121.192501. Fulltekst i vitenarkiv Vis sammendrag

  The lifetimes of the first excited 2þ, 4þ, and 6þ states in 98Zr were measured with the recoil-distance Doppler shift method in an experiment performed at GANIL. Excited states in 98Zr were populated using the fission reaction between a 6.2 MeV=u 238U beam and a 9 Be target. The γ rays were detected with the EXOGAM array in correlation with the fission fragments identified by mass and atomic number in the VAMOS++ spectrometer. Our result shows a very small BðE2; 2þ 1 → 0þ 1 Þ value in 98Zr, thereby confirming the very sudden onset of collectivity at N ¼ 60. The experimental results are compared to large-scale Monte Carlo shell model and beyond-mean-field calculations. The present results indicate the coexistence of two additional deformed shapes in this nucleus along with the spherical ground state.

• Kaya, L.; Vogt, A.; Reiter, Peter; Müller-Gatermann, C.; Siciliano, M. & Coraggio, L [Vis alle 62 forfattere av denne artikkelen] (2018). Millisecond 23/2+ isomers in the N=79 isotones 133Xe and 135Ba. Physical Review C. ISSN 2469-9985. 98(5). doi: 10.1103/PhysRevC.98.054312. Fulltekst i vitenarkiv Vis sammendrag

  Detailed information on isomeric states in A ≈ 135 nuclei is exploited to benchmark shell-model calculations in the region northwest of doubly magic nucleus 132Sn. The N = 79 isotones 133Xe and 135Ba are studied after multinucleon transfer in the 136Xe + 208Pb reaction employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and in a pulsed-beam experiment at the FN tandem accelerator of the University of Cologne, Germany utilizing a 9 Be + 130Te fusion-evaporation reaction at a beam energy of 40 MeV. Isomeric states are identified via delayed γ -ray spectroscopy. Hitherto tentative excitation energy, spin, and parity assignments of the 2107-keV J π = 23/2+ isomer in 133Xe are confirmed and a half-life of T1/2 = 8.64(13) ms is measured. The 2388-keV state in 135Ba is identified as a J π = 23/2+ isomer with a half-life of 1.06(4) ms. The new results show a smooth onset of isomeric J π = 23/2+ states along the N = 79 isotones and close a gap in the high-spin systematics towards the recently investigated J π = 23/2+ isomer in 139Nd. The resulting systematics of M2 reduced transition probabilities is discussed within the framework of the nuclear shell model. Latest large-scale shell-model calculations employing the SN100PN, GCN50:82, SN100-KTH, and a realistic effective interaction reproduce the experimental findings generally well and give insight into the structure of the isomers.

• Garrote, Frank Leonel Bello; Görgen, Andreas; Mihai, C.; Abraham, T.; Campo, Lucia Crespo & Delaroche, Jean Paul [Vis alle 34 forfattere av denne artikkelen] (2018). Lifetime measurements in 138Nd. Physical Review C. ISSN 2469-9985. 97(6), s. 1–7. doi: 10.1103/PhysRevC.97.064310. Fulltekst i vitenarkiv Vis sammendrag

  Lifetimes of several short-lived excited states in 138Nd were measured with the ROSPHERE array at IFIN-HH, Bucharest, using the recoil-distance Doppler shift technique following the 123Sb(19F,4n) reaction. The resulting electromagnetic transition probabilities are compared to large-scale shell model calculations and to constrained Hartree-Fock-Bogoliubov calculations with the Gogny D1S interaction, configuration mixing, and a five-dimensional collective Hamiltonian formalism. The onset of collectivity in Nd isotopes below the N = 82 shell closure and the deformation induced by the alignment of protons and neutron holes in the h11/2 orbitals are discussed.

• Kaya, L.; Vogt, A.; Reiter, Peter; Siciliano, M.; Birkenbach, B. & Blazhev, A [Vis alle 70 forfattere av denne artikkelen] (2018). High-spin structure in the transitional nucleus 131Xe: Competitive neutron and proton alignment in the vicinity of the N=82 shell closure. Physical Review C. ISSN 2469-9985. 98(1). doi: 10.1103/PhysRevC.98.014309. Fulltekst i vitenarkiv Vis sammendrag

  The transitional nucleus 131Xe is investigated after multinucleon transfer in the 136Xe + 208Pb and 136Xe + 238U reactions employing the high-resolution Advanced γ -Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and as an elusive reaction product in the fusion-evaporation reaction 124Sn(11B,p3n) 131Xe employing the High-efficiency Observatory for γ -Ray Unique Spectroscopy (HORUS) γ -ray array coupled to a double-sided silicon strip detector at the University of Cologne, Germany. The level scheme of 131Xe is extended to 5 MeV. A pronounced backbending is observed at hω¯ ≈ 0.4 MeV along the negative-parity one-quasiparticle νh11/2(α = −1/2) band. The results are compared to the high-spin systematics of the Z = 54 isotopes and the N = 77 isotones. Large-scale shell-model calculations employing the PQM130, SN100PN, GCN50:82, SN100-KTH, and a realistic effective interaction reproduce the experimental findings and provide guidance to elucidate the structure of the high-spin states. Further calculations in 129−132Xe provide insight into the changing nuclear structure along the Xe chain towards the N = 82 shell closure. Proton occupancy in the π 0h11/2 orbital is found to be decisive for the description of the observed backbending phenomenon.

• Hadynska-Klek, Katarzyna; Napiorkowski, Paweł Jan; Zielinska, Magdalena; Srebrny, Julian; Maj, Adam & Azaiez, Faisal [Vis alle 110 forfattere av denne artikkelen] (2018). Quadrupole collectivity in 42Ca from low-energy Coulomb excitation with AGATA. Physical Review C. ISSN 2469-9985. 97:024326(2), s. 1–20. doi: 10.1103/PhysRevC.97.024326. Fulltekst i vitenarkiv Vis sammendrag

  A Coulomb-excitation experiment to study electromagnetic properties of 42Ca was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in 42Ca were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in 42Ca, including the diagonal E2 matrix elements of 2+ 1 and 2+ 2 states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 0+ 1,2 and 2+ 1,2 states, as well as triaxiality for 0+ 1,2 states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in 42Ca. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in 42Ca.

• Yokoyama, R.; Ideguchi, E.; Simpson, G.S.; Tanaka, Mn.; Nishimura, S. & Doornenbal, P. [Vis alle 52 forfattere av denne artikkelen] (2018). Beta-gamma spectroscopy of the neutron-rich ¹⁵⁰Ba. Progress of Theoretical and Experimental Physics. 2018(4), s. 1–8. doi: 10.1093/ptep/pty037. Fulltekst i vitenarkiv
• Wilson, Joshua N.; Lebois, Matthieu; Qi, Liqiang; Amador-Celdran, Pedro; Bleuel, Darren L. & Briz, José A. [Vis alle 49 forfattere av denne artikkelen] (2018). Studies of fission fragment yields via high-resolution γ-ray spectroscopy. The European Physical Journal Conferences. ISSN 2101-6275. 169, s. 1–8. doi: 10.1051/epjconf/201816900030. Fulltekst i vitenarkiv Vis sammendrag

  Precise spectroscopic information on the fast neutron induced fission of the 238U(n,f) reaction was recently gained using a new technique which involved coupling of the Miniball high resolution y-ray spectrometer and the LICORNE directional neutron source. The experiment allowed measurement of the isotopic fission yields for around 40 even-even nuclei at an incident neutron energy of around 2 MeV where yield data are very sparse. In addition spectroscopic information on very neutron-rich fission products was obtained. Results were compared to models, both the JEFF-3.1.1 data base and the GEF code, and large discrepancies for the S1 fission mode in the Sn/Mo isotope pair were discovered. This suggests that current models are overestimating the role played by spherical shell effects in fast neutron induced fission. In late 2017 and 2018 the nu-ball hybrid spectrometer will be constructed at the IPN Orsay to perform further experimental investigations with directional neutrons coupled to a powerful hybrid Ge/LaBr3 detector array. This will open up new possibilities for measurements of fission yields for fast-neutron-induced fission using the spectroscopic technique and will be complimentary to other methods being developed.

• Wimmer, Kathrin; Korten, Wolfram; Arici, Tugba; Doornenbal, Pieter C.; Aguilera, Pablo & Algora, Alexandro [Vis alle 34 forfattere av denne artikkelen] (2018). Shape coexistence and isospin symmetry in A = 70 nuclei: Spectroscopy of the Tz = -1 nucleus 70Kr. Physics Letters B. ISSN 0370-2693. 785, s. 441–446. doi: 10.1016/j.physletb.2018.07.067. Fulltekst i vitenarkiv Vis sammendrag

  Excited states in the Tz = −1 nucleus 70Kr have been populated using inelastic scattering of a radioactive 70Kr beam as well as one- and two-neutron removal reactions from 71,72Kr at intermediate beam energies. The level scheme of 70Kr was constructed from the observed γ -ray transitions and coincidences. Tentative spin and parity assignments were made based on comparison with the mirror nucleus 70Se. A second 2+ state and a candidate for the corresponding 4+ 2 state suggest shape coexistence in 70Kr.

• Sua, Martha Liliana Cortés; Doornenbal, P; Dupuis, M; Lenzi, SM; Nowacki, F & Obertelli, A [Vis alle 68 forfattere av denne artikkelen] (2018). Inelastic scattering of neutron-rich Ni and Zn isotopes off a proton target. Physical Review C. ISSN 2469-9985. 97(4), s. 1–10. doi: 10.1103/PhysRevC.97.044315. Fulltekst i vitenarkiv Vis sammendrag

  Proton inelastic scattering of 72,74Ni and 76,80Zn ions at energies around 235 MeV/nucleon was performed at the Radioactive Isotope Beam Factory and studied using γ -ray spectroscopy. Angular integrated cross sections for direct inelastic scattering to the 2+ 1 and 4+ 1 states were measured. The Jeukenne-Lejeune-Mahaux folding model, extended beyond 200 MeV, was used together with neutron and proton densities stemming from quasiparticle random-phase approximation (QRPA) calculations to interpret the experimental cross sections and to infer neutron to proton matrix element ratios. In addition, coupled-channels calculations with a phenomenological potential were used to determine deformation lengths. For the Ni isotopes, correlations favor neutron excitations, thus conserving the Z = 28 gap. A dominance of proton excitation, on the other hand, is observed in the Zn isotopes, pointing to the conservation of the N = 50 gap approaching 78Ni. These results are in agreement with QRPA and large-scale shell-model calculations.

• Morales, Ana Isabel; Benzoni, G; Watanabe, H; Angelis, G de; Nishimura, S & Coraggio, L [Vis alle 63 forfattere av denne artikkelen] (2018). Is seniority a partial dynamic symmetry in the first νg9/2 shell? Physics Letters B. ISSN 0370-2693. 781, s. 706–712. doi: 10.1016/j.physletb.2018.04.049. Fulltekst i vitenarkiv Vis sammendrag

  The low-lying structures of the midshell ν g9/2 Ni isotopes 72Ni and 74Ni have been investigated at the RIBF facility in RIKEN within the EURICA collaboration. Previously unobserved low-lying states were accessed for the first time following β decay of the mother nuclei 72Co and 74Co. As a result, we provide a complete picture in terms of the seniority scheme up to the first (8+) levels for both nuclei. The experimental results are compared to shell-model calculations in order to define to what extent the seniority quantum number is preserved in the first neutron g9/2 shell. We find that the disappearance of the seniority isomerism in the (8+ 1 ) states can be explained by a lowering of the seniority-four (6+) levels as predicted years ago. For 74Ni, the internal de-excitation pattern of the newly observed (6+ 2 ) state supports a restoration of the normal seniority ordering up to spin J = 4. This property, unexplained by the shell-model calculations, is in agreement with a dominance of the single-particle spherical regime near 78Ni.

• Campo, Lucia Crespo; Guttormsen, Magne Sveen; Garrote, Frank Leonel Bello; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Vis alle 15 forfattere av denne artikkelen] (2018). Test of the generalized Brink-Axel hypothesis in 64,65Ni. Physical Review C. ISSN 2469-9985. 98, s. 054303-1–054303-10. doi: 10.1103/PhysRevC.98.054303. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Liu, XY; Liu, Zhong; Ding, B; Doornenbal, P; Obertelli, A & Lenzi, SM [Vis alle 78 forfattere av denne artikkelen] (2018). Spectroscopy of 25,65/67Mn: Strong coupling in the N = 40 "island of inversion". Physics Letters B. ISSN 0370-2693. 784, s. 392–396. doi: 10.1016/j.physletb.2018.06.067. Fulltekst i vitenarkiv Vis sammendrag

  Excited states in 63,65,67Mn were studied via in-beam γ -ray spectroscopy following knockout reactions from 68Fe. Similar level schemes, consisting of the 11/2−, 9/2−, 7/2− and 5/2− g.s. level sequence, connected by I → I − 1 transitions, were established, the first time for 65,67Mn. Their level structures show features consistent with strongly-coupled rotational bands with K = 5/2. State-of-the-art shellmodel calculations with the modified LNPS effective interaction reproduce the observed levels remarkably well and suggest the dominance of 4-particle-4-hole neutron configurations for all the states. The data on the low-lying excited states of odd-mass 53−67Mn provide a textbook example of nuclear structure evolution from weak coupling through decoupling to strong coupling along a single isotopic chain on the n-rich side of the β stability line. These results help to deepen our understanding of the N = 40 “island of inversion”.

• Morales, Ana Isabel; Benzoni, Giovanna; Watanabe, Hiroshi; Tsunoda, Yusuke; Otsuka, Takaharu & Nishimura, Shunji [Vis alle 55 forfattere av denne artikkelen] (2017). Type II shell evolution in A = 70 isobars from the N ≥ 40 island of inversion. Physics Letters B. ISSN 0370-2693. 765, s. 328–333. doi: 10.1016/j.physletb.2016.12.025. Fulltekst i vitenarkiv
• Brits, C.P.; Wiedeking, M.; Garrote, Frank Leonel Bello; Bleuel, D. L.; Giacoppo, F. & Görgen, Andreas [Vis alle 22 forfattere av denne artikkelen] (2017). Resonances in odd-odd 182Ta. The European Physical Journal Conferences. ISSN 2101-6275. 146. doi: 10.1051/epjconf/201714605012. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Klintefjord, Malin Linnea; Ljungvall, Joa; Görgen, Andreas; Lenzi, Silvia M.; Garrote, Frank Leonel Bello & Blazhev, Andrey [Vis alle 60 forfattere av denne artikkelen] (2017). Measurement of lifetimes in 62,64Fe, 61,63Co and 59Mn. Physical Review C. ISSN 2469-9985. 95(2). doi: 10.1103/PhysRevC.95.024312. Fulltekst i vitenarkiv
• Hagen, Trine Wiborg; Görgen, Andreas; Korten, W.; Grente, L; Salsac, MD & Farget, F [Vis alle 29 forfattere av denne artikkelen] (2017). Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions. Physical Review C. ISSN 2469-9985. 95(3). doi: 10.1103/PhysRevC.95.034302. Fulltekst i vitenarkiv
• Sumikama, Toshiyuki; Nishimura, Shunji; Baba, Hidetada; Browne, Fiona; Doornenbal, Pieter C. & Fukuda, Naoki [Vis alle 40 forfattere av denne artikkelen] (2017). Observation of new neutron-rich Mn, Fe, Co, Ni, and Cu isotopes in the vicinity of Ni 78. Physical Review C. ISSN 2469-9985. 95(5). doi: 10.1103/PhysRevC.95.051601. Fulltekst i vitenarkiv
• Shand, Callum Macintyre; Podolyák, Zsolt; Górska, Magda; Doornenbal, Pieter C.; Obertelli, Alexandre & Nowacki, Frédéric [Vis alle 96 forfattere av denne artikkelen] (2017). Shell evolution beyond Z = 28 and N = 50: Spectroscopy of 81,82,83,84Zn. Physics Letters B. ISSN 0370-2693. 773, s. 492–497. doi: 10.1016/j.physletb.2017.09.001. Fulltekst i vitenarkiv
• Patel, Z.; Walker, P.M.; Podolyák, Zsolt; Regan, P.H.; Berry, T.A. & Söderström, Pär Anders [Vis alle 58 forfattere av denne artikkelen] (2017). Isomer-delayed γ-ray spectroscopy of A=159-164 midshell nuclei and the variation of K-forbidden E1 transition hindrance factors. Physical Review C. ISSN 2469-9985. 96(3). doi: 10.1103/PhysRevC.96.034305. Fulltekst i vitenarkiv
• Malatji, Kgashane L.; Kheswa, Bonginkosi Vincent; Wiedeking, M.; Garrote, Frank Leonel Bello; Brits, C.P. & Bleuel, D. L. [Vis alle 21 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

Se alle arbeider i NVA

• Sahin, Eda (2026). When magic numbers stop being magic. Fulltekst i vitenarkiv Vis sammendrag

  Public outreach lecture on the structure of atomic nuclei and the evolution of nuclear shell closures. The lecture introduced the concept of nuclear magic numbers and discussed how shell structure can change in exotic, neutron-rich nuclei far from stability.

• Sahin, Eda (2026). Spectroscopy of exotic nuclei. Fulltekst i vitenarkiv
• Ingeberg, Vetle Wegner; Görgen, Andreas; Inoue, Azusa; Kumar, Neeraj; Larsen, Ann-Cecilie & Li, Kevin Ching Wei [Vis alle 9 forfattere av denne artikkelen] (2026). OSCAR at ISOLDE. Fulltekst i vitenarkiv Vis sammendrag

  For the next run period at ISOLDE, the Nuclear Physics group at the University of Oslo are considering proposing a longer experimental campaign with the Oslo SCintillator ARay (OSCAR). The main aims of such a campaign will be to measure the nuclear level density and -ray strength function of key nuclei relevant for nuclear structure and nuclear astrophysics (e.g. i-process nucleosynthesis). Other cases of interest could be spectroscopy of resonances in light exotic nuclei or rare event searches. In addition, we would also invite other interested groups to propose experiments with the setup while it is present at HIE-ISOLDE. The OSCAR array is the largest LaBr:Ce detector array in the world (at least in terms of detector volume). It offers exceptional efficiency for high-energy -rays without compromising on either energy or time resolution. It consists of 30 large 3.5x8-inch large volume LaBr3:Ce detectors, an icosahedron frame with six rings covering polar angles from to . Detectors can be mounted in a distance of 16.3 to 22 cm from the target, resulting in solid angle coverage of 57%. This translates to about 15% full energy efficiency at 1332 keV and close to 5% at 10 MeV in the closest configuration. In this presentation I will present the physics cases and our preliminary plans for such a campaign.

• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Vis alle 15 forfattere av denne artikkelen] (2026). CLUSTER'26. Fulltekst i vitenarkiv
• Sahin, Eda (2024). Evolution of shapes and collectivity in the 78Ni mass region. Fulltekst i vitenarkiv
• Sahin, Eda (2024). Shell evolution and shape coexistence in exotic nuclei. Fulltekst i vitenarkiv
• Sahin, Eda (2023). Gamma-ray spectroscopy of exotic neutron-rich nuclei. Fulltekst i vitenarkiv
• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Vis alle 20 forfattere av denne artikkelen] (2023). Remeasuring the gamma-decay branching ratio of the Hoyle state. Fulltekst i vitenarkiv
• Sahin, Eda (2023). Research Theme 1: Nuclear Properties. Fulltekst i vitenarkiv

Se alle arbeider i NVA