Observation of high-spin oblate band structures inPm141

Abstract

The high-spin states of $^{141}\mathrm{Pm}$ have been investigated through the reaction $^{126}\mathrm{Te}$($^{19}\mathrm{F}$,4$n$) at a beam energy of 90 MeV. A previous level scheme has been updated with spins up to 49/2$\ensuremath{\hbar}$. Six collective bands at high spins are newly observed. Based on the systematic comparison, one band is proposed as a decoupled band; two bands with strong $\ensuremath{\Delta}I=1$ $M1$ transitions inside the bands are suggested as the oblate bands with $\ensuremath{\gamma}$ $~$$\ensuremath{-}{60}^{\ifmmode^\circ\else\textdegree\fi{}}$; three other bands with large signature splitting have been proposed with the oblate-triaxial deformation with $\ensuremath{\gamma}$$~$ $\ensuremath{-}{90}^{\ifmmode^\circ\else\textdegree\fi{}}$. The triaxial $n$-particle-$n$-hole particle rotor model calculations for one of the oblate bands in $^{141}\mathrm{Pm}$ are in good agreement with the experimental data. The other characteristics for these bands have been discussed.