Octupole deformation in two-quasiparticle states of even–even deformed nuclei

Abstract

Following the Skyrme-Hartree–Fock-BCS approach with blocking to two-quasiparticle states describing K-isomeric states of deformed even–even nuclei as presented in an earlier work of some of us Minkov N et al (2022 Phys. Rev. C 105 044 329), we study the emergence of axial-octupole deformation in excited states of this nature. We select two representative nuclei in the rare-earth and actinide mass regions, namely 148Ce (octupole-deformed in its ground state) and 234U (with a left-right symmetric ground-state shape), and several low-lying two-quasiparticle configurations illustrating cases where, in the same nucleus, some such excited states are calculated to be octupole deformed and some others are not. Then we investigate the mechanism favoring the appearance of left-right asymmetric shapes in the two-quasiparticle excited states of one-particle-one-hole type. We find in particular that strong octupole coupling between the blocked hole and particle states of a two-quasiparticle configuration does not favor pear-like shapes. In contrast, octupole coupling of the blocked particle (resp. hole) state with another particle (resp. hole) state located slightly above (resp. below) it in the single-particle spectrum favors pear-like shapes in the two-quasiparticle state.