New high-spin level schemes and excitation modes of 117,118,119,120,122Cd

Abstract

Abstract High-spin level schemes of 117,118,119,120,122 Cd are expanded by analyzing our high-statistics triple- and higher-fold coincidence events of prompt fission γ rays from 252 Cf at Gammasphere. Spin/parity assignments were made based on new γ – γ angular correlation measurements and level systematics in the neighboring isotopes. Stretch-aligned band structures observed in low-lying levels in 117,119,121 Cd are seen to weaken with increasing spins, with a quasi-rotational degree of freedom manifested at higher spins. The 5 − levels in even- N 118,120 Cd were tentatively interpreted as candidates of quadrupole–octupole (QOC) coupling. The model-independent spin versus ℏω curves for even- N and odd- N Cd isotopes imply quasi-rotational alignment of an h 11 / 2 neutron pair in the even- N Cd isotopes. The relative energies of the lowest 11 / 2 − , 9 / 2 − , 7 / 2 − , and 15 / 2 − levels in 117 Cd and 119 Cd suggest triaxial shapes based on Meyer-Ter-Vehn theory for these odd- N Cd nuclei. For the even- N Cd isotopes evidence of triaxiality may also be provided by the Shell Correction version of the Tilted Axis Cranking model (SCTAC).