Collective oblate band in La 131 due to the rotational alignment of h 1 1 / 2 neutrons

TLDR: Several rotational bands have been populated to high spin in the \ensuremath{\gamma}-soft nucleus $^{131}\mathrm{La}$ with expreimental evidence for a collective oblate rotational band based on a three-quasiparticle configuration.

Abstract: Several rotational bands have been populated to high spin in the \ensuremath{\gamma}-soft nucleus $^{131}\mathrm{La}$. We present expreimental evidence for a collective oblate rotational band based on a \ensuremath{\pi}${\mathrm{h}}_{11/2}$\ensuremath{\bigotimes}(\ensuremath{\nu}${\mathrm{h}}_{11/2}$${)}^{2}$ three-quasiparticle configuration. It is the rotational alignment of the pair of neutrons from the upper ${\mathrm{h}}_{11/2}$ midshell which drives the nucleus from a prolate (\ensuremath{\gamma}=0\ifmmode^\circ\else\textdegree\fi{}) shape to a collectively rotating oblate (\ensuremath{\gamma}=-60\ifmmode^\circ\else\textdegree\fi{}) shape. This band coexists with a prolate band that contains a pair of aligned protons from the lower ${\mathrm{h}}_{11/2}$ midshell.