Multi-quasiparticle excitations of⁹¹Ru

Abstract：

The level structure in neutron-deficient nucleus ⁹¹Ru was investigated via the ⁵⁸Ni ( ³⁶Ar, 2 p1 n $\gamma $ ) ⁹¹Ru reaction at a beam energy of 111 MeV. Charged particles, neutrons, and $\gamma $ -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 $N=47$ isotone. These excitations have been interpreted in terms of the shell model. The calculations performed in the configuration space $(p_{3/2},f_{5/2},p_{1/2},g_{9/2})$ reproduce the experimental excitation energies reasonably well, supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurations $\pi(g_{9/2})^{-2} \nu(g_{9/2})^{-1}$ and $\nu (g_{9/2})^{-3}$ .