Speaker
Description
The nuclei, characterized by large $N/Z$ ratios, are often referred to as exotic nuclei and challenge the traditional understanding of nuclear shell structure. The conventional magic numbers, such as $N=$8, 20, 28, etc., tend to diminish or vanish, and new magic numbers emerge in the exotic systems. In this work, we investigated the appearance of new magic numbers at $N=32$ and 34 and their evolution in neutron-rich isotopes lying above and below Ca. We studied the shell gaps from the underlying two- and three-nucleon forces obtained from QCD-based chiral effective field theory, employing the state-of-the-art ab initio valence-space in-medium similarity renormalization group method. The development of shell gaps at $N=32$ and 34 is discussed from various nuclear observables and effective single-particle energies. Our calculated results align well with the available experimental data and suggest a strengthening of the $N=34$ sub-shell gap while the $N=32$ sub-shell gap weakens or disappears below Ca. To understand the microscopic origin of these shell effects, we analyzed different components of the nuclear interaction -central, spin-orbit, and tensor- through spin-tensor decomposition and elucidated their roles in establishing shell gaps far from stability. Then, the low-energy structures of the exotic $N=32$ isotones, adjacent to the $N=34$ shell gap, are studied in detail. It is observed that these nuclei exhibit deformed ground states and coexist with a weakly deformed band at low-excitation energy. The present work demonstrates essential components of nuclear force in shaping magic numbers far from stability and offers deeper insights into the structure of exotic nuclei from the underlying nucleon-nucleon interactions.
| Research field of your presentation | Theoretical Low-energy nuclear physics |
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