Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieliska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.
European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08
The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0, 2, and 4 states was observed in all nuclei under study. Reduced matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
Kaya, L.*; Vogt, A.*; Reiter, P.*; Siciliano, M.*; 清水 則孝*; 宇都野 穣; Wang, H.-K.*; Gargano, A.*; Coraggio, L.*; Itaco, N.*; et al.
Physical Review C, 100(2), p.024323_1 - 024323_18, 2019/08
Queiser, M.*; Vogt, A.*; Seidlitz, M.*; Reiter, P.*; 富樫 智章*; 清水 則孝*; 宇都野 穣; 大塚 孝治*; 本間 道雄*; Petkov, P.*; et al.
Physical Review C, 96(4), p.044313_1 - 044313_13, 2017/10
Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.
Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06
Radioactive ion beams of Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2 to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
Diriken, J.*; Patronis, N.*; Andreyev, A.; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physical Review C, 91(5), p.054321_1 - 054321_15, 2015/05
Excited states up to an excitation energy of 5.8 MeV were populated in the neutron-rich isotope Ni via the Ni(d,p) transfer reaction at REX-Isolde, CERN. In particular, single-neutron states above the N=40 sub-shell gap were populated, and the relative spectroscopic factors were extracted using distorted-wave Born approximation analysis. The positive parity g, d and s neutron orbits above the shell closure are assumed to induce strong quadrupole collectivity in neutron-rich Fe and Cr isotopes. The extracted relative spectroscopic factors show that the strength of the d orbit is mostly split over two states, hinting to substantial mixing of the neutron d configuration with collective modes of the core. The size of the N=50 shell gap was also estimated, and found to be 2.6 MeV near Ni, as also determined in lighter Ni isotopes.
Sahin, E.*; Doncel, M.*; Sieja, K.*; De Angelis, G.*; Gadea, A.*; Quintana, B.*; Grgen, A.*; Modamio, V.*; Mengoni, D.*; Valiente-Dobn, J. J.*; et al.
Physical Review C, 91(3), p.034302_1 - 034302_9, 2015/03
The level structure of the neutron-rich Cu, Cu, and Cu isotopes was investigated using multinucleon transfer reactions at Laboratori Nazionali di Legnaro using the AGATA Demonstrator array coupled to the PRISMA magnetic spectrometer. Lifetimes of excited states in Cu nuclei were measured with the recoil-distance Doppler-shift method. The resulting electromagnetic matrix elements for transitions from excited states in Cu nuclei was used to assess the collective or single-particle character of these states. The results are compared with predictions of large-scale shell-model calculations, showing how the proton pf shell evolve as neutrons fill the 1g orbital.
Diriken, J.*; Patronis, N.*; Andreyev, A. N.*; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physics Letters B, 736, p.533 - 538, 2014/09
The neutron orbits , d and s are assumed to be responsible for the swift onset of collectivity observed in the region below Ni. In order to gather information on the single-particle energies and spectroscopic factors of these orbitals, single-particle states in the nucleus Ni were populated using the reaction Ni(d,p), in inverse kinematics, at REX-ISOLDE, CERN. The new isotope was studied using combined particle- spectroscopy. Comparison with DWBA calculations, permitted the identification of positive parity states with a substantial amount of d (1007 keV) and d (2207 and 3277 keV) single-particle strength. Comparisons with extended Shell-Model calculations was also performed to confirm the single-particle nature of these states, and to deduce general properties around Ni.