Octupole states in deformed actinide nuclei with the interacting boson approximation

Abstract

Octupole states have been studied systematically in the deformed actinide nuclei ${}^{230}\mathrm{Th},$ ${}^{234,236,238}\mathrm{U},$ ${}^{240}\mathrm{Pu},$ ${}^{246}\mathrm{Cm},$ and ${}^{250}\mathrm{Cf}$ using the interacting boson approximation 1. Parameters for the positive parity cores were set by reproducing data from the ground state and \ensuremath{\gamma}-vibration bands with the extended consistent-$Q$ formalism. A prescription for setting the parameter ${\ensuremath{\epsilon}}_{f}$ systematically was adopted for the calculations of the octupole bands. The ordering of the ${K}^{\ensuremath{\pi}}{=0}^{\ensuremath{-}},$ ${1}^{\ensuremath{-}},$ and ${2}^{\ensuremath{-}}$ bands and the behavior of many $E1$ and $E3$ transitions are well reproduced with a narrow range of parameters, particularly when the existence of a $N=164$ subshell gap is assumed. It is predicted that in ${}^{246}\mathrm{Cm}$ and ${}^{250}\mathrm{Cf}$ the ${K}^{\ensuremath{\pi}}{=3}^{\ensuremath{-}}$ octupole states built on the ground state are located above 6 MeV and are strongly fragmented.