Triaxial projected shell model study of γ-bands in atomic nuclei

A systematic study of gamma-bands observed in atomic nuclei is performed using the triaxial projected shell model (TPSM) approach. The staggering phase between the even and odd spin members of the. -band for most of the nuclei investigated in the present work is found to have even-I-below-odd-I, which in the framework of the collective model is considered as a signature of gamma-softness. It is observed that out of twenty-three systems studied, only four nuclei, namely, Ge-76, Ru-112, Er-170 and Th-232 depict staggering phase with odd-I-below-even-I, which is regarded as an indication of the static gamma-deformation in the collectivemodel picture. The inclusion of the quasiparticle excitations in the framework of configuration mixing is shown to reverse the staggering phase from odd-I-down to the even-I-down for all the studied nuclei, except for the aforementioned four nuclei. Furthermore, by fitting a collective Bohr Hamiltonian to the TPSM energies, the differences between the two models are delineated through a comparison of the transition probabilities.