Octupole correlations in stable nucleus¹⁵³Eu within reflection-asymmetric particle rotor model

Abstract：

The observed low-lying $K=5/2^\pm$ positive- and negative-parity bands in the stable nucleus ¹⁵³Eu are investigated using the reflection-asymmetric triaxial particle rotor model. The experimental energy spectra, energy staggering parameters, and intraband $E2$ and $M1$ transition probabilities are well reproduced. The calculated interband $B(E1)$ values are found to depend sensitively on the octupole deformation parameter $\beta_{30}$ , although the energy spectra and intraband $E2$ and $M1$ transitions can be reproduced without the octupole degree of freedom. The observed enhanced $E1$ transition probabilities can be reproduced with $\beta_{30}=0.05$ . The detailed analysis of the intrinsic wave functions shows these nearly degenerate positive- and negative-parity bands are built on two individual proton configurations, i.e., dominated by $\pi g_{7/2}[\Omega=5/2]$ and $\pi h_{11/2}[\Omega=5/2]$ , respectively, which differs from the parity doublet bands built on a single parity-mixed configuration.