Low-lying structure and shape evolution in neutron-rich Se isotopes

Rapid CommunicationsInternational audienceNeutron-rich $^{88,90,92,94}$ Se isotopes were studied via in-beam $\gamma$-ray spectroscopy after nucleon removal reactions at intermediate energies at the Radioactive Isotope Beam Factory. Based on gamma-gamma coincidence analysis, low-lying excitation level schemes are proposed for these nuclei, including the 2$_1^+$, 4$_1^+$ states and 2$_2^+$ states at remarkably low energies. The low-lying 2$_2^+$ states, along with other features, indicate triaxiality in these nuclei. The experimental results are in good overall agreement with self-consistent beyond-mean-field calculations based on the Gogny D1S interaction, which suggests both triaxial degree of freedom and shape coexistence playing important roles in the description of intrinsic deformations in neutron-rich Se isotopes

First Indication for Shape Transitions in Neutron-rich Selenium Isotopes

Neutron-rich 88,90,92,94Se isotopes were studied via in-beam γ-ray spectroscopy after production from nucleon removal at intermediate energies at the Radioactive Isotope Beam Factory. γ-γ coincidence analysis allowed to establish level schemes for the first time in these nuclei, including the 2+ 1 → 0 + gs, 4+ 1 → 2 + 1 transitions and their energy ratio R4/2. Low-lying 2+ 2 levels and their branching to the 2+ 1 and 0+ gs states were observed. The experimental results are in good agreement with self-consistent beyond-mean-field calculations based on the Gogny D1S interaction, suggesting ground state shape transition from oblate to prolate then back to oblate between N = 52 − 60 and indicating shape coexistence

Triaxiality of neutron-rich 84;86;88Ge from low-energy nuclear spectra

-ray transitions between low-spin states of the neutron-rich 84;86;88Ge were measured by means of in-flight -ray spectroscopy at 270 MeV/u. Excited 6+ 1 , 4+ 1;2 and 2+ 1;2 states of 84;86Ge and 4+ 1 and 2+ 1;2 states of 88Ge were observed. Furthermore a candidate for a 3+ 1 state of 86Ge was identified. This state plays a key role in the discussion of ground-state triaxiality of 86Ge, along with other features of its low-energy level scheme. A new region of triaxially deformed nuclei is proposed in the Ge isotopic chain

First Indication for Shape Transitions in Neutron-rich Selenium Isotopes

Neutron-rich 88,90,92,94Se isotopes were studied via in-beam γ-ray spectroscopy after production from nucleon removal at intermediate energies at the Radioactive Isotope Beam Factory. γ-γ coincidence analysis allowed to establish level schemes for the first time in these nuclei, including the 2+ 1 → 0 + gs, 4+ 1 → 2 + 1 transitions and their energy ratio R4/2. Low-lying 2+ 2 levels and their branching to the 2+ 1 and 0+ gs states were observed. The experimental results are in good agreement with self-consistent beyond-mean-field calculations based on the Gogny D1S interaction, suggesting ground state shape transition from oblate to prolate then back to oblate between N = 52 − 60 and indicating shape coexistence

Triaxiality of neutron-rich 84,86,88Ge from low-energy nuclear spectra

γ-ray transitions between low-spin states of the neutron-rich 84,86,88Ge were measured by means of in-flight γ-ray spectroscopy at 270 MeV/u. Excited 6+1,4+1,2, and 2+1,2 states of 84,86Ge and 4+1 and 2+1,2 states of 88Ge were observed. Furthermore, a candidate for a 3+1 state of 86Ge was identified. This state plays a key role in the discussion of ground-state triaxiality of 86Ge, along with other features of its low-energy level scheme. A new region of triaxially deformed nuclei is proposed in the Ge isotopic chain.status: publishe