Onset of intruder ground state in exotic Na isotopes and evolution of the N=20 shell gap

Abstract

The onset of intruder ground states in Na isotopes is investigated by comparing experimental data and shell-model calculations. This onset is one of the consequences of the disappearance of the N=20 magic structure, and the Na isotopes are shown to play a special role in clarifying the change of this magic structure. Both the electromagnetic moments and the energy levels clearly indicate an onset of ground state intruder configurations at neutron number N=19 already, which arises only with a narrow N=20 shell gap in Na isotopes resulting from the spin-isospin dependence of the nucleon-nucleon interaction (as compared to a wider gap in stable nuclei like 40Ca). It is shown why the previous report based on the mass led to a wrong conclusion.

9 pages, 6 figures, to be published in Phys. Rev. C

References in corpus (4)

• Magic numbers in exotic nuclei and spin-isospin properties of {\it NN} interaction
• New effective interaction for $pf$-shell nuclei and its implications for the stability of the $N$=$Z$=28 closed core
• Effective interaction for pf-shell nuclei
• Nuclear Shell Model by the Quantum Monte Carlo Diagonalization Method

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