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تسجيل مستخدم جديدLarge scale shell model calculations along Z=28 and N=50 closures: towards the doubly-magic 78Ni
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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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The evolution of the N=50 gap is analyzed as a function of the occupation of the proton f5/2 and p3/2 orbits. It is based on experimental atomic masses, using three different methods of one or two-neutron separation energies of ground or isomeric sta
tes. We show that the effect of correlations, which is maximized at Z=32 could be misleading with respect to the determination of the size of the shell gap, especially when using the method with two-neutron separation energies. From the methods that are the least perturbed by correlations, we estimate the N=50 spherical shell gap in 78Ni. Whether 78Ni would be a rigid spherical or deformed nucleus is discussed in comparison with other nuclei in which similar nucleon-nucleon forces are at play.
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We present a procedure that is helpful to reduce the computational complexity of large-scale shell-model calculations, by preserving as much as possible the role of the rejected degrees of freedom in an effective approach. Our truncation is driven fi
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Nuclei with magic numbers serve as important benchmarks in nuclear theory. In addition, neutron-rich nuclei play an important role in the astrophysical rapid neutron-capture process (r-process). 78Ni is the only doubly-magic nucleus that is also an i
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