High-spin states of ${}^{89}\mathrm{Sr}$ and ${}^{90}\mathrm{Sr}$ were studied via the reactions ${}^{82}\mathrm{Se}{(}^{11}\mathrm{B},$ $p3n)$ and ${}^{82}\mathrm{Se}{(}^{11}\mathrm{B},$ $p2n),$ respectively, at a beam energy of 37 MeV. Gamma rays were detected with the GASP spectrometer. The level schemes of ${}^{89}\mathrm{Sr}$ and ${}^{90}\mathrm{Sr}$ were extended up to $E\approx 8$ MeV and $E\approx 10$ MeV, respectively. Level structures in ${}^{89}\mathrm{Sr}$ and ${}^{90}\mathrm{Sr}$ were interpreted in terms of the spherical shell model. The calculations were 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. High-spin level sequences in ${}^{89}\mathrm{Sr}$ are characterized by coupling the unpaired $d_{5/2}$ neutron to proton excitations of the core nucleus ${}^{88}\mathrm{Sr}.$ An equidistant level sequence with $\Delta J=2\mathrm{}$ found in ${}^{90}\mathrm{Sr}$ is well described by the configuration $\pi \left[{(0f}_{5/2}^{-2}{\left)\right(0g}_{9/2}^2\right)\left]\nu {(1d}_{5/2}^2\right)$ favoring even spins.

• Received 15 February 2001

DOI:https://doi.org/10.1103/PhysRevC.63.064315