Octupole collectivity in the Sm isotopes

Abstract

Microscopic models suggest the occurrence of strong octupole correlations in nuclei with $N\ensuremath{\approx}88$. To examine the signatures of octupole correlations in this region, the spdf interacting boson approximation model is applied to Sm isotopes with $N=86\text{\ensuremath{-}}92$. The effects of including multiple negative-parity bosons in this basis are compared with more standard one negative-parity boson calculations and are analyzed in terms of signatures for strong octupole correlations. It is found that multiple negative-parity bosons are needed to describe properties at medium spin. Bands with strong octupole correlations (multiple negative-parity bosons) become yrast at medium spin in $^{148,150}\mathrm{Sm}$. This region shares some similarities with the light actinides, where strong octupole correlations were also found at medium spin.