Structure of high-spin states in 89Sr and 90Sr

High-spin states of ⁸⁹Sr and ⁹⁰Sr were studied via the reactions ⁸²Se(¹¹B, p3n) and ⁸²Se(¹¹B, p2n), respectively, at a beam energy of 37 MeV. Gamma rays were detected with the GASP spectrometer. The level schemes of ⁸⁹Sr and ⁹⁰Sr were extended up to E~8 MeV and E~10 MeV, respectively. Level structures in ⁸⁹Sr and ⁹⁰Sr 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 ⁸⁹Sr are characterized by coupling the unpaired d_5/2 neutron to proton excitations of the core nucleus ⁸⁸Sr. An equidistant level sequence with ΔJ=2 found in ⁹⁰Sr is well described by the configuration π[(0f^{- 2}_5/2)(0g²_9/2)]ν(1d²_5/2) favoring even spins.