Abstract : The decays of two isomeric states in the neutron-rich nucleus Cu75 have been studied via delayed γ-ray spectroscopy. These states were populated by the fragmentation of a 60.4AMeV Kr86 primary beam, which impinged on a Be target at the LISE2k spectrometer of GANIL. Isomeric half-lives and branching ratios were measured, and a γ−γ coincidence analysis performed. These have allowed a revised level scheme of Cu75 to be proposed. A comparison with large-scale shell-model calculations using different effective interactions and valence spaces shows the importance of proton excitations across the Z=28 shell gap for reproducing the energy spacing between the isomeric states. The coexisting collective and single-particle properties of the (1/2−) and (3/2−) states, respectively, are similar to those of the same states in the neighboring Cu69,71,73. The small energy spacings between the (1/2−), (3/2−), and 5/2− states are responsible for the isomerism.
