Wobbling excitations in 156Dy and 162Yb

Abstract

We study in the cranked Nilsson plus random phase approximation low-lying quadrupole excitations of positive parity and negative signature in 156Dy and 162Yb at high spins. Special attention is paid to a consistent description of wobbling excitations and their identification among excited states. A good agreement between available experimental data and the results of calculations is obtained. We found that in 156Dy the lowest odd spin gamma-vibrational states transform to the wobbling excitations after the backbending, associated with the transition from axially-symmetric to nonaxial shapes. Similar results are predicted for 162Yb. The analysis of electromagnetic transitions, related to the wobbling excitations, determines uniquely the sign of the gamma-deformation in 156Dy and 162Yb after the transition point.