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 h _{11}/{2}{7}/{2}^-[523] yrast and g _{7}/{2}{7}/{2}⁺[404] side bands have been extracted from measured γ-ray angular correlations. Lifetimes of excited states in the yrast and the decoupled h _{9}/{2}{1}/{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}^-1[541] band has a significatly 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.