Signature splitting inversion and backbending in80Rb

Abstract

High-spin states of ${}^{80}$Rb are studied via the fusion-evaporation reactions ${}^{65}$Cu+${}^{19}$F, ${}^{66}$Zn+${}^{18}$O, and ${}^{68}$Zn+${}^{16}$O with the beam energies of 75 MeV, 76 MeV, and 80 MeV, respectively. Twenty-three states with twenty-eight \ensuremath{\gamma} transitions are added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22${}^{\ensuremath{-}}$ and 15${}^{\ensuremath{-}}$ and two sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the \ensuremath{\alpha} $=$ 0 branch as well as another one in the \ensuremath{\alpha} $=$ 1 branch of the second negative-parity band are observed. Signature inversions occur in the positive-parity and first negative-parity bands at the spins of 11$\ensuremath{\hbar}$ and 16$\ensuremath{\hbar}$, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone ${}^{82}$Y. Signature inversion in the positive-parity yrast band with configuration \ensuremath{\pi}${g}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{g}_{9/2}$ in this nucleus is discussed using the projected shell model.