Shell structure, emerging collectivity, and valence p-n interactions

R.B Cakirli,S Lunardi,M Chiari,J.J Valiente-Dobon,R Menegazzo,A Dainese,P Di Nezza,C Bucci,P.G Bizzeti,A Nannini,C Signorini

doi:10.1051/epjconf/20146601019

Abstract

The structure of atomic nuclei depends on the interactions of its constituents, protons and neutrons. These interactions play a key role in the development of configuration mixing and in the onset of collectivity and deformation, in changes to the single particle energies and magic numbers, and in the microscopic origins of phase transitional behavior. Particularly important are the valence proton-neutron interactions which can be studied experimentally using double differences of binding energies extracted from high-precision mass measurements. The resulting quantities, called δV pn , are average interaction strengths between the last two protons and the last two neutrons. Focusing on the Z=50-82, N=82-126 shells, we have considered a number of aspects of these interactions, ranging from their relation to the underlying orbits, their behaviour near close shells and throughout major shells, their relation to the onset of collectivity and deformation, and the appearance of unexpected spikes in δV pn values for a special set of heavy nuclei with nearly equal numbers of valence protons and neutrons. We have calculated spatial overlaps between proton and neutron Nilsson orbits and compared these with the experimental results. Finally we also address the relation between masses (separation energies), changes in structure and valence nucleon number.

Highlights

AND AVERAGE PROTON-NEUTRON INTERACTIONSAND EMERGING COLLECTIVITYThe numbers of protons and neutrons and/or valence protons and neutrons can guide us in understanding special properties about a nucleus or a nuclear region such as the onset of deformation, shape changes and so on
Focusing on the Z=50-82, N=82-126 shells, we have considered a number of aspects of these interactions, ranging from their relation to the underlying orbits, their behaviour near close shells and throughout major shells, their relation to the onset of collectivity and deformation, and the appearance of unexpected spikes in δVpn values for a special set of heavy nuclei with nearly equal numbers of valence protons and neutrons
The average valence proton-neutron interactions, δVpn, which can be studied experimentally using double differences of binding energies extracted from high-precision mass measurements, are discussed from both experimental and theoretical perspectives by focusing on the Z=50-82, N=82-126 shells

Summary

AND EMERGING COLLECTIVITY

The numbers of protons and neutrons and/or valence protons and neutrons can guide us in understanding special properties about a nucleus or a nuclear region such as the onset of deformation, shape changes and so on. One can see, in particular, shell effects at the magic numbers, or the onset of deformation, for example in the N~90 region. The p-n interaction is important because it helps to understand, for example, magic numbers, deformation, single particle energies, collectivity, and the development of configuration mixing. Shows this special filter for p-n interactions using binding energies, B, for even-even nuclei

Po Ra

SCHOTTKY MASS MEASUREMENTS

CONCLUSION