High-spin excitations of the odd-odd ⁸⁸ ₃₇Rb₅₁ and ⁸⁶ ₃₅Br₅₁ nuclei: $\pi$p_3/2 $\nu$d_5/2 and $\pi$f_5/2 $\nu$d_5/2 residual interactions

Abstract

The odd-odd ⁸⁸ ₃₇Rb₅₁ and ⁸⁶ ₃₅Br₅₁ nuclei have been produced as fission fragments in the fusion reaction

¹⁸O$ + $²⁰⁸Pb

at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the triple $\gamma$ -ray coincidence data and $\gamma$ -$\gamma$ angular correlations have been analyzed in order to assign spin and parity values to many observed states. The proposed configurations involve proton excitations from three sub-shells located close to the Fermi levels, $\pi$ p _3/2 , $\pi$ f _5/2 , and $\pi$ g _9/2 , the $\nu$ d _5/2 neutron acting as a spectator. The residual $\pi$ $\nu$ interactions are extracted from the multiplets of states resulting from the $\pi$ p _3/2 $\nu$ d _5/2 and $\pi$ f _5/2 $\nu$ d _5/2 configurations. The empirical values of the latter are discussed and compared to those known in two similar configurations having j _p = j _n with l _p = l _n + 1 , where the role of the tensor force had been highlighted.