Alternating-parity bands of U236,238 and Pu238,240 in a particle-number-conserving method based on the cranked shell model

Abstract

The particle-number-conserving (PNC) method in the framework of cranked shell model (CSM) is developed to deal with the reflection-asymmetric nuclear system by applying the ${S}_{x}$ symmetry. Based on an octupole-deformed Nilsson potential, the alternating-parity bands in $^{236,238}\mathrm{U}$ and $^{238,240}\mathrm{Pu}$ are investigated. The experimental kinematic moments of inertia (MoI) and the angular momentum alignments of all studied bands are reproduced well in the PNC-CSM calculations. The striking difference of rotational behaviors between U and Pu isotopes can be linked to the strength of octupole correlations. The upbendings of the alternating-parity bands in $^{236,238}\mathrm{U}$ are due to the alignments of pairs of nucleons occupying $\ensuremath{\nu}{g}_{9/2}, \ensuremath{\pi}{f}_{7/2}$ orbitals and $\ensuremath{\nu}{j}_{15/2}, \ensuremath{\pi}{i}_{13/2}$ high-$j$ intruder orbitals. In particular, the interference terms of nucleon occupying the octupole-correlation pairs of ${\ensuremath{\nu}}^{2}{j}_{15/2}{g}_{9/2}$ and of ${\ensuremath{\pi}}^{2}{i}_{13/2}{f}_{7/2}$ give a very important contribution to the suddenly gained alignments.