Structure of high-spin states in Sr-91 and Sr-92

Abstract

The nuclei Sr-91 and Sr-92 were produced at high spin as fission fragments following the fusion reaction S-36+Tb-159 at 165 MeV. gamma rays were detected with the Gammasphere array. The level schemes of Sr-91 and Sr-92 were extended up to Eapproximate to6 MeV and Eapproximate to8 MeV, respectively. Level structures in Sr-91 and Sr-92 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 Sr-92 is discussed.