Triaxiality and exotic rotations at high spins inCe134

Abstract

High-spin states in $^{134}\mathrm{Ce}$ have been investigated using the $^{116}\mathrm{Cd}(^{22}\mathrm{Ne},4n)$ reaction and the Gammasphere array. The level scheme has been extended to an excitation energy of $\ensuremath{\sim}30$ MeV and spin $\ensuremath{\sim}54\phantom{\rule{0.16em}{0ex}}\ensuremath{\hbar}$. Two new dipole bands and four new sequences of quadrupole transitions were identified. Several new transitions have been added to a number of known bands. One of the strongly populated dipole bands was revised and placed differently in the level scheme, resolving a discrepancy between experiment and model calculations reported previously. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. A coherent understanding of the various excitations, both at low and high spins, is thus obtained, supporting an interpretation in terms of coexistence of stable triaxial, highly deformed, and superdeformed shapes up to very high spins. Rotations around different axes of the triaxial nucleus, and sudden changes of the rotation axis in specific configurations, are identified, further elucidating the nature of high-spin collective excitations in the $A=130$ mass region.