Lifetimes and electromagnetic transition strengths in 155 Dy

Recoil distance Doppler-shift and Doppler-shift attenuation lifetime measurements were carried out for levels in ${}^{155}$Dy through the coincident detection of $\ensuremath{\gamma}$ rays. Twenty-six lifetimes, most of them for the first time, were determined using the differential decay curve method for the analysis of the data. At low and medium spins, particle-plus-triaxial-rotor calculations reveal different quadrupole deformations for the one-quasineutron bands in this transitional nucleus. At high spin, the reduced $B(E2)$ transition probabilities confirm with a better precision the results of a previous study implying decreased collectivity with increasing spin.