Collective γ-vibrational bands in 165Ho and 167Er

The nuclear structures of 165Ho and 167Er have been investigated by means of Coulomb excitation. These nuclei excited at moderate spins exhibit γ-vibrational bands with Kπ = 112−,32− in 165Ho and Kπ = 112+ in 167Er. The γ-vibrational bands in 165Ho are found to be isospectral; heaving very nearly identical in-band γ-ray energies. Gamma-ray branching ratios are analysed to extract information on collectivity and Coriolis mixing. Experimental results are compared with calculations performed with the Cranked Shell Moedl + RPA + particle-vibration coupling and by invoking the generalized intensity relations (GIR) in the unified model scheme. Although this model explains many features of the data, puzzling aspects such as identical transition energies for the bands in 165Ho remain unexplained. The role of the K quantum number in identical bands is discussed.