Transition quadrupole moments in γ-soft nuclei and the triaxial projected shell model

Transition probabilities of the ground-state bands in γ-soft nuclei are studied for the first time using the triaxial projected shell model approach. It is observed that the angular-momentum dependence of the transition quadrupole moment Qt is related to the triaxial deformation of the nuclear mean-field potential. The introduction of the γ-degree of freedom in the shell model basis is shown to have a little influence on the constant behavior of the low-spin Qt in a well-deformed nucleus. However, the increasing collectivity with spin for the low-spin states in a γ-soft nucleus can only be explained by considering the triaxial mean-field deformation.