2023/03/29 by Y. Omura, H. Nakada, Omura, Y. +5
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Nuclear Materials and Properties #Nuclear Physics and Applications #Nuclear Theory (nucl-th) #Nuclear physics research studies
paper · pdf · doi:10.48550/arxiv.2303.16483
openalex publication_date 2023/03/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Quadrupole collectivity of the lowest-lying states, focusing on Ex(2+1) and B(E2;0+1→ 2+1), have been investigated for the N=50-82 Sn nuclei by applying the self-consistent approaches with the semi-realistic interaction M3Y-P6. Both Ex(2+1) and B(E2;0+1→ 2+1) are well reproduced by the spherical Hartree-Fock-Bogolyubov (HFB) plus quasiparticle random-phase approximation (QRPA) calculations in N≥ 64, without adjustable parameters. The measured B(E2) values in the neutron-deficient Sn nuclei cast a puzzle. In 54≤ N≤ 62, the spherical HFB + QRPA calculations give too strong B(E2), opposite to the shell-model predictions within the one major shell. Via the constrained-HFB (CHFB) calculations, it is found that the neutron-deficient Sn nuclei are soft against the quadrupole deformation, accounting for the limited applicability of the HFB + QRPA approach. In particular, the potential energy curves (PECs) are almost flat in the range of |q0|\lesssim 200 fm2 in 106-110Sn. We confirm that the near degeneracy of n0g7/2 and n1d5/2 triggers weak quadrupole deformation and its balance with the pairing makes PECs flat, which is qualitatively consistent with a recent shell model result in an extended model space, by the calculations shifting the single-particle energy spacing and the pairing strength. These conclusions are supported by the proton-to-neutron ratios of the transition matrix elements and the reference values of B(E2) with the angular-momentum projection on top of the CHFB solutions.