Rotational bands in 133Ce.

Abstract

Several rotational bands built on one- and three-quasiparticle configurations have been populated in the odd-neutron $^{133}\mathrm{Ce}$ nucleus following the $^{119}\mathrm{Sn}$${(}^{18}$O,4n) reaction. Both signature components of bands built on the [514]${(9/2}^{\mathrm{\ensuremath{-}}}$ and [400]${(1/2}^{+}$ orbitals were observed. At low spins, the yrast band, based on a neutron from the upper ${h}_{11/2}$ midshell, shows a large signature splitting (>100 keV), indicating a significant triaxial deformation (\ensuremath{\gamma}\ensuremath{\sim}-20\ifmmode^\circ\else\textdegree\fi{}). Four \ensuremath{\Delta}I=1 bands were observed at higher spins based on three-quasiparticle configurations. Strong M1 transitions and the lack of signature splitting imply that these bands are near prolate (\ensuremath{\gamma}\ensuremath{\sim}0\ifmmode^\circ\else\textdegree\fi{}) and thus contain one or more aligned ${h}_{11/2}$ protons from the lower midshell. In two of these bands, weak E2 crossover transitions were seen; measured B(M1;I\ensuremath{\rightarrow}I-1)/B(E2;I\ensuremath{\rightarrow}I-2) ratios were used to assign configurations. In addition, a \ensuremath{\Delta}I=2 band with an enhanced moment of inertia was observed most probably built on the prolate \ensuremath{\nu}${i}_{13/2}$\ensuremath{\bigotimes}[\ensuremath{\pi}${h}_{11/2}$${]}^{2}$ configuration. Only one signature component of this configuration was seen because of the maximal signature splitting of the \ensuremath{\beta}-driving ${i}_{13/2}$ neutron orbital (\ensuremath{\Omega}=(1/2).