The nuclei ${}^{91}\mathrm{Sr}$ and ${}^{92}\mathrm{Sr}$ were produced at high spin as fission fragments following the fusion reaction ${}^{36}\mathrm{S}{+}^{159}\mathrm{Tb}$ at 165 MeV. $\gamma$ rays were detected with the Gammasphere array. The level schemes of ${}^{91}\mathrm{Sr}$ and ${}^{92}\mathrm{Sr}$ were extended up to $E\approx 6\hspace{0.5em}\mathrm{MeV}$ and $E\approx 8\hspace{0.5em}\mathrm{MeV},$ respectively. Level structures in ${}^{91}\mathrm{Sr}$ and ${}^{92}\mathrm{Sr}$ were interpreted in shell-model calculations performed in the configuration space ${(0f}_{5/2}{,1p}_{3/2}{,1p}_{1/2}{,0g}_{9/2})$ for the protons and ${(1p}_{1/2}{,0g}_{9/2}{,1d}_{5/2})$ for the neutrons. Negative-parity states in the yrast sequences are described in these calculations by coupling $3^{-}$ proton excitations to the unpaired ${1d}_{5/2}$ neutrons. A possible reduction of the gap between the proton ${1p}_{3/2}$ and ${1p}_{1/2}$ orbitals in ${}^{92}\mathrm{Sr}$ is discussed.

• Received 10 October 2001

DOI:https://doi.org/10.1103/PhysRevC.65.034323