Multi-quasiparticle excitations of 91Ru *

Abstract The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni (36Ar, 2p1n ) 91Ru reaction at a beam energy of 111 MeV. Charged particles, neutrons, and -rays were emitted in this reaction and detected by the DIAMANT CsI ball, Neutron Wall, and the EXOGAM Ge clover array, respectively. In addition to the previously reported levels in 91Ru, new low-to-medium spin states were observed. Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91Ru. The low-spin states of 91Ru exhibit a scheme of multi-quasiparticle excitations, which is very similar to that of the neighboring isotone. These excitations have been interpreted in terms of the shell model. The calculations performed in the configuration space reproduce the experimental excitation energies reasonably well, supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurations and .