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

High-spin level schemes of 117,118,119,120,122Cd are expanded by analyzing our high-statistics triple- and higher-fold coincidence events of prompt fission γ rays from 252Cf 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 117,119,121Cd are seen to weaken with increasing spins, with a quasi-rotational degree of freedom manifested at higher spins. The image levels in even-N 118,120Cd 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 image neutron pair in the even-N Cd isotopes. The relative energies of the lowest image, image, image, and image levels in 117Cd and 119Cd 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).