Quenching of the E1 strength in 149Nd

Abstract

Lifetime measurements of excited states in 149Nd have been performed using the advanced time-delayed \( \beta\)\( \gamma\)\( \gamma\)(t) method. Half-lives of 14 excited states in 149Nd have been determined for the first time or measured with higher precision. Twelve new \( \gamma\) -lines and 5 new levels have been introduced into the decay scheme of 149Pr based on results of the \( \gamma\)\( \gamma\) coincidence measurements. Reduced transition probabilities have been determined for 40 \( \gamma\) -transitions in 149Nd . Configuration assignments for 6 rotational bands in 149Nd are proposed. Enhanced E1 transitions indicate that the ground-state band and the band built on the 332.9keV level constitute a pair of the \(\ensuremath K^{\pi} = 5/2^{\pm}\) parity doublet bands. Potential energy surfaces on the \(\ensuremath (\beta_{2},\beta_{3})\) -plane have been calculated for the lowest single quasi-particle configurations in 149Nd using the Strutinski method and the axially deformed Woods-Saxon potential. The predicted occurrence of the octupole-deformed K = 5/2 configuration is in agreement with experiment. Unexpectedly low \(\ensuremath \vert D_0\vert\) values obtained for the \(\ensuremath K^{\pi} = 5/2^{\pm}\) parity doublet bands may result from cancellation between the proton and neutron shell correction contributions to \(\ensuremath \vert D_0\vert\) .