Two new high-lying level sequences of negative parity have been identified in the odd-proton nucleus ${}_{}{}^{81}{}_{}{}^{}\mathrm{Rb}$ by in-beam γ-ray spectroscopy using the reactions ${}_{}{}^{79}{}_{}{}^{}\mathrm{Br}$(α,2n) at 27 MeV and ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}$${(}^{19}$F,α2n) at 72 MeV. One sequence, dominated by M1 transitions, is interpreted as a three-quasiparticle band predominantly containing a neutron in the ${\mathit{p}}_{1/2}$, ${\mathit{p}}_{3/2}$, or ${\mathit{f}}_{5/2}$ subshell coupled to ${\mathit{g}}_{9/2}$ proton and ${\mathit{g}}_{9/2}$ neutron excitations. The other new level sequence forms the three-quasiparticle extension of the unfavored negative-parity band, but the states decay also by E1 transitions. The signature splitting points to a configuration where an aligned ${\mathit{g}}_{9/2}$ proton pair is involved.

• Received 28 February 1994

DOI:https://doi.org/10.1103/PhysRevC.50.1845