Large scale shell model calculations along Z=28 and N=50 closures: towards the doubly-magic 78Ni

We present the state-of-the art shell model calculations in a large model space (pf for protons, fpgd for neutrons), which allow to study simultaneously excitations across the Z=28 and N=50 shell gaps. We explore the region in the vicinity of 78Ni, being a subject of intense experimental investigations. Our calculations account correctly for the known low lying excited states in this region, including those which may correspond to cross-shell excitations. We observe the minimum of the N=50 mass gap at Z=32 consistent with experimental data and its further increase towards Z=28, indicating a robustness of the N=50 gap in 78Ni. The evolution of N=50 gap along the nickel chain is shown to bear similarities with what is know in oxygen and calcium chains, providing a new opportunity for the studies of 3-body monopole effects in medium mass nuclei.

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