Lifetimes of yrast and near-yrast states of /sup 159,160,161/Yb

Lifetimes of high-spin states of /sup 159,160,161/Yb, populated by fusion-evaporation reactions, have been measured by the recoil-distance technique. The data were collected in coincidence with a total-energy filter to provide some discrimination on reaction channel. The principal feature of the resulting transition quadrupole moments is a frequency-dependent reduction which is displayed by those bands with aligned quasiparticles. This seems to be mainly due to the influence of the favored i/sub 13/2/ quasineutron. Additional available data are surveyed and support this conclusion. Calculations using the cranked shell model and the cranked Hartree-Fock-Bogoliubov and cranked Nilsson-Strutinsky methods provide a qualitative description of the experimental observations. In addition, a satisfactory account is provided by recent calculations based on a fermion dynamical-symmetry model.