Structure of the low-lying intrinsic states in 156Eu.

Abstract

Microscopic structures of the low-lying nonrotational (intrinsic) states in the odd-odd nucleus $_{63}^{156}\mathrm{Eu}_{93}$ are investigated using the quasiparticle-phonon nuclear model Hamiltonian including the pairing, quadrupole-quadrupole, octupole-octupole, and residual p-n interactions. The extent of vibrational admixtures to the two-quasiparticle configurations and the intrinsic matrix elements of electric octupole operator for the ``same K opposite parity'' bands are examined to conclude that, contrary to some recent suggestions, the low-energy $^{156}\mathrm{Eu}$ spectrum does not contain ``parity doublets'' characteristic of reflection asymmetric shapes, in contrast with the structures seen in $^{152}\mathrm{Eu}$ and $^{154}\mathrm{Eu}$.