Eur. Phys. J. A (2026) 62: 70
https://doi.org/10.1140/epja/s10050-026-01806-7

Regular Article - Experimental Physics

Lifetimes of negative parity states in $_{}^{162}$Dy

¹ Department of Physics and Astronomy, University of Notre Dame, 46556, Notre Dame, IN, USA
² Department of Physics, North Carolina A&T State University, 27411, Greensboro, NC, USA
³ Department of Physics, University of Wisconsin–La Crosse, 54601, La Crosse, WI, USA
⁴ Department of Physics and Astronomy, Mississippi State University, 39762, Starkville, MS, USA
⁵ Department of Chemistry, University of Kentucky, 40506, Lexington, KY, USA
⁶ Department of Physics and Astronomy, University of Kentucky, 40506, Lexington, KY, USA

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Received: 16 October 2025
Accepted: 30 January 2026
Published online: 3 April 2026

Abstract

Lifetimes of excited states in $_{}^{162}$Dy were measured using the (n,n’$\gamma$) 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^π = 2_1,2^- bands decaying to the the K$_{}^{\pi }=2_{\gamma }^{+}$ band, consistent with signatures of octupole-quadrupole coupling. In contrast, the K$_{}^{\pi }=0_1^{-}$ and K$_{}^{\pi }=1_3^{-}$ 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 $_{}^{162}$Dy as the most extensively characterized rare-earth nucleus for negative parity lifetimes and provide critical experimental benchmarks for theoretical models.