Study the nuclear structure for some nuclei in the island of inversion region using the shell model and Hartree-Fock calculations

Abstract

The study of neutron-rich nuclei around and in Nuclear Island of Inversion region (N ≈ 20) offers critical insights into shell evolution, the erosion of traditional magic numbers, and the emergence of intruder configurations. In this work, we investigate the static and dynamic nuclear structure properties of Al, Na, and F isotopes through a combination of large-scale shell model calculations. Shell model calculations were performed in the sd-shell model space using the USDA, USDB, and USDC effective interactions, and in a truncated no-core spsdpf model space using the FSU interaction, determined in this study. Key observables such as excitation energies, B(E2) transition probabilities, binding energies, two-neutron separation energies, shell evolution, and longitudinal C2 electroexcitation form factors were systematically analyzed. The results demonstrate that while traditional sd-shell interactions are inadequate for capturing the enhanced collectivity and cross-shell excitations characteristic of the island of inversion, the FSU interaction provide a much-improved description of the evolving shell structure.