Configuration-dependent transition rates in 161Tm

High-spin states in 161Tm were populated using the reaction 128Te(37Cl,4n) at a beam energy of 167 MeV. The M1/E2 mixing ratios of transitions in the strongly coupled h11/27/2-[523[ yrast and g7/27/2+[404[ side bands have been extracted from measured γ-ray angular correlations. Lifetimes of excited states in the yrast and the decoupled h9/21/2-[541[ sequences have been measured using the recoil-distance method and absolute reduced transition probabilities have been extracted. The results are compared to predictions of various nuclear models. It is shown that the 1/2-[541[ band has a significantly larger quadrupole deformation than the yrast sequence. The observed B(M1;I→I-1) values in the yrast band and the B(M1)/B(E2) ratios for ΔI=1 transitions in both strongly-coupled bands are consistent with a zero or small negative triaxial deformation. (orig.)