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• Pedersen, Line Gaard; Sahin, Eda; Görgen, Andreas; Garrote, Frank Leonel Bello; Tsunoda, Y. & Otsuka, T. [Show all 67 contributors for this article] (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. Full text in Research Archive Show summary

  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 [Show all 17 contributors for this article] (2026). Exploring the statistical properties of the neutron-deficient 109In isotope with the Oslo method. Physical Review C. ISSN 2469-9985. 113(4). doi: 10.1103/qrvh-s12k. Full text in Research Archive Show summary

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

• Heines, J. S.; Modamio, Victor; Görgen, A.; Korten, W.; Clément, E. & Dudouet, J. [Show all 29 contributors for this article] (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. Full text in Research Archive Show summary

  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.

• Heines, Johannes Sørby; Modamio, Victor; Görgen, Andreas; Korten, Wolfram; Ljungvall, Joa & Pasqualato, G. [Show all 45 contributors for this article] (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. Full text in Research Archive Show summary

  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.

• Gheorghe, I.; Goriely, S.; Wagner, N.; Aumann, T.; Baumann, M. & Beek, Beek Van [Show all 19 contributors for this article] (2024). Photoneutron cross section measurements on Pb 208 in the giant dipole resonance region. Physical Review C. ISSN 2469-9985. 110(1). doi: 10.1103/PhysRevC.110.014619. Full text in Research Archive
• Pasqualato, G; Ansari, S.; Heines, Johannes Sørby; Modamio, Victor; Görgen, Andreas & Beckmann, Kristine Sønstevold [Show all 52 contributors for this article] (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. Full text in Research Archive Show summary

  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. [Show all 67 contributors for this article] (2023). First spectroscopic study of odd-odd Cu 78. Physical Review C. ISSN 2469-9985. 107(4). doi: 10.1103/PhysRevC.107.044301. Full text in Research Archive Show summary

  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.

• Pedersen, Line Gaard; Sahin, Eda; Görgen, Andreas; Garrote, Frank Leonel Bello; Tsunoda, Yusuke & Otsuka, Takaharu [Show all 67 contributors for this article] (2023). Experimental Level Scheme of 78Cu. Acta Physica Polonica B. ISSN 0587-4254. 16. doi: 10.5506/APhysPolBSupp.16.4-A14. Full text in Research Archive
• Pogliano, Francesco; Larsen, Ann-Cecilie; Goriely, Stéphane; Siess, Lionel; Markova, Maria & Görgen, Andreas [Show all 17 contributors for this article] (2023). Experimentally constrained Ho 165,166 (n,γ) rates and implications for the s process. Physical Review C. ISSN 2469-9985. 107(6). doi: 10.1103/PhysRevC.107.064614. Full text in Research Archive
• Pogliano, Francesco; Garrote, Frank Leonel Bello; Larsen, Ann-Cecilie; Berg, Hannah Christine; Gjestvang, Dorthea & Görgen, Andreas [Show all 19 contributors for this article] (2023). Observation of a candidate for the M1 scissors resonance in odd-odd Ho 166. Physical Review C. ISSN 2469-9985. 107(3). doi: 10.1103/PhysRevC.107.034605. Full text in Research Archive Show summary

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

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

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

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

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

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

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

• Butler, P.A.; Gaffney, L.P.; Abrahams, K.; Bowry, M.; Cederkäll, J. & Chupp, T. [Show all 43 contributors for this article] (2022). Coulomb excitation of Rn 222. Physical Review C. ISSN 2469-9985. 105(2). doi: 10.1103/PhysRevC.105.024323. Full text in Research Archive Show summary

  The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3− and 2+→5− transitions were found to be respectively 2360+300−210efm3 and 2300+300−500efm3 while a smaller value, 1200+500−900efm3, was found for the 2+→1− transition. In addition, four excited non-yrast states were identified in this work via γ−γ coincidences.

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

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

• Butler, P.A.; Gaffney, L.P.; Spagnoletti, P.; Konki, J.; Scheck, M. & Smith, J.F. [Show all 44 contributors for this article] (2020). Addendum: The observation of vibrating pear-shapes in radon nuclei. Nature Communications. 11(1), p. 3560–3560. doi: 10.1038/s41467-020-17309-y. Full text in Research Archive
• Butler, Peter A.; Gaffney, LP; Spagnoletti, P.; Abrahams, K.; Bowry, M. & Cederkall, Joakim [Show all 43 contributors for this article] (2020). Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive 222Ra and 228Ra Beams. Physical Review Letters. ISSN 0031-9007. 124(4). doi: 10.1103/PhysRevLett.124.042503. Full text in Research Archive Show summary

  There is sparse direct experimental evidence that atomic nuclei can exhibit stable “pear” shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in 222,228Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing 222Ra as pear shaped with stable octupole deformation, while 228Ra behaves like an octupole vibrator.

• Butler, P.A.; Gaffney, L.P.; Spagnoletti, P.; Konki, J.; Scheck, M. & Smith, J.F. [Show all 44 contributors for this article] (2019). The observation of vibrating pear-shapes in radon nuclei. Nature Communications. 10:2473, p. 1–6. doi: 10.1038/s41467-019-10494-5. Full text in Research Archive Show summary

  There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we observed the low-lying quantum states in 224Rn and 226Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.

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• Heines, Johannes Sørby; Görgen, Andreas; Modamio, Victor & Pedersen, Line Gaard (2021). Shape evolution in neutron-rich fission fragments in the mass A=100 region. Full text in Research Archive
• Butler, P.A.; Gaffney, L.P.; Spagnoletti, P.; Konki, J.; Scheck, M. & Smith, J.F. [Show all 44 contributors for this article] (2020). Publisher Correction: The observation of vibrating pear-shapes in radon nuclei (Nature Communications, (2019), 10, 1, (2473), 10.1038/s41467-019-10494-5). Nature Communications. 11(1). doi: 10.1038/s41467-020-19081-5. Full text in Research Archive

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