High-spin bands in 80Kr.

Abstract

High-spin states in $^{80}\mathrm{Kr}$ were studied using the $^{65}\mathrm{Cu}$${(}^{18}$O,p2n) reaction at 65 MeV. Prompt \ensuremath{\gamma}-\ensuremath{\gamma} coincidences were measured using the Pitt-FSU detector array with nine high-purity Compton-suppressed Ge detectors and a 28-element Bismuth Germanate multiplicity filter. The previous level scheme has been extended by 16 new states up to spins and parities of ${20}^{+}$ and (${19}^{\mathrm{\ensuremath{-}}}$). The known band crossing in the positive-parity yrast band of $^{80}\mathrm{Kr}$ near \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\approxeq}0.5 MeV may be due to a ${\mathit{g}}_{9/2}$ neutron alignment, rather than a ${\mathit{g}}_{9/2}$ proton alignment as had been previously thought, based on the predicted oblate shape by Hartree-Fock-Bogolyubov calculations. No evidence was found for a second crossing in the yrast sequence up to \ensuremath{\Elzxh}\ensuremath{\omega}=0.9 MeV. The new extension of the ground-state band through nonyrast states points to another band crossing at \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\approxeq}0.62 MeV which may be caused by a ${\mathit{g}}_{9/2}$ proton alignment. A new negative-parity high-spin band shows that rotational bands do form at excitations above the strongly mixed low-spin levels as in the isotone $^{82}\mathrm{Sr}$.