Lifetimes of negative parity states in 162Dy

Lifetimes of excited states in 162Dy were measured using the (n,n’γ) reaction with the Doppler-Shift Attenuation Method (DSAM) at the University of Kentucky’s Accelerator Laboratory. A total of eighteen level lifetimes were obtained, including eleven negative-parity states, seven of which are new. These measurements significantly expand the experimental database of transition probabilities for negative-parity bands in the well-deformed rare earth region of nuclei. The extracted B(E1) and B(E2) values reveal enhanced interband E1 (10-3 or 10-4) W.u. and E2 strengths (several W.u.) between negative- and positive parity bands, particularly for the K bands decaying to the the Kπ=2γ+ band, consistent with signatures of octupole-quadrupole coupling. In contrast, the Kπ=01- and Kπ=13- bands, which exhibit strong E1 transitions to the ground state band, are indicative of octupole-vibrational excitations built on the deformed ground state. Comparison of transition rates with Alaga rules supports this interpretation and distinguishes collective excitations from likely quasi-particle states. These new results establish 162Dy as the most extensively characterized rare-earth nucleus for negative parity lifetimes and provide critical experimental benchmarks for theoretical models.