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

Abstract Lifetimes of excited states in $$^{162}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>162</mml:mn> </mml:mmultiscripts> </mml:math> Dy were measured using the (n,n’ $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> ) 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 ( $$10^{-3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> or $$10^{-4}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:math> ) 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 $$^{\pi }=2^+_{\gamma }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mi>π</mml:mi> </mml:mmultiscripts> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mn>2</mml:mn> <mml:mi>γ</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> band, consistent with signatures of octupole-quadrupole coupling. In contrast, the K $$^{\pi }=0^-_1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mi>π</mml:mi> </mml:mmultiscripts> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mn>0</mml:mn> <mml:mn>1</mml:mn> <mml:mo>-</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> and K $$^{\pi }=1^-_3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mi>π</mml:mi> </mml:mmultiscripts> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mn>1</mml:mn> <mml:mn>3</mml:mn> <mml:mo>-</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> 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 $$^{162}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>162</mml:mn> </mml:mmultiscripts> </mml:math> Dy as the most extensively characterized rare-earth nucleus for negative parity lifetimes and provide critical experimental benchmarks for theoretical models.