Lifetimes of negative parity states in ¹⁶²Dy

Lifetimes of excited states in ¹⁶² 162 Dy were measured using the (n,n’ γ 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( E 1) and B( E 2) values reveal enhanced interband E1 ( 10⁻³ 10 - 3 or 10⁻⁴ 10 - 4 ) W.u. and E2 strengths (several W.u.) between negative- and positive parity bands, particularly for the K"Equation missing" bands decaying to the the K π=2⁺γ π = 2 γ + band, consistent with signatures of octupole-quadrupole coupling. In contrast, the K π=0⁻₁ π = 0 1 - and K π=1⁻₃ π = 1 3 - 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 ¹⁶² 162 Dy as the most extensively characterized rare-earth nucleus for negative parity lifetimes and provide critical experimental benchmarks for theoretical models.