Shell-model approach to the low-energy spectrum of ⁵⁹Cu

A standard shell-model calculation was carried out for the low lying levels of ⁵⁹Cu. The three outer nucleons, outside the ⁵⁶Ni core, are allowed to move in the 1p 3 2, Of 5 2 and 1p 1 2 single particle orbits. A conventional gaussian interaction with exchange character is taken as residual interaction. Treating the strength of the interaction as a parameter, it is not possible to get agreement with experiment for any of the four exchange mixtures which we consider. The main discrepancy is found for the large f 5 2 single particle strength observed in the excited level at 0.92 MeV. Repeating the calculation with the SDI and treating the triplet strength as a parameter, it becomes possible to obtain a satisfactory fit for all data if one assumes the 1.83 and 1.96 MeV levels to be due to configurations which are neglected in this calculation.