Tensor-optimized shell model for the Li isotopes with a bare nucleon-nucleon interaction

TL;DR

This paper employs the tensor-optimized shell model with a bare nucleon-nucleon interaction to analyze the role of tensor forces in the spectra of Li isotopes, revealing their significant impact on energy levels and state configurations.

Contribution

It introduces a systematic study of Li isotopes using TOSM combined with UCOM, highlighting the tensor force's influence on nuclear spectra with a novel approach.

Findings

Tensor force causes characteristic effects on spectra.

Energy differences in 5Li are due to tensor correlations.

Low-lying states in 7-9Li are influenced by tensor contributions.

Abstract

We study the Li isotopes systematically in terms of the tensor-optimized shell model (TOSM) by using a bare nucleon-nucleon interaction as the AV8' interaction. The short-range correlation is treated in the unitary correlation operator method (UCOM). Using the TOSM+UCOM approach, we investigate the role of the tensor force on each spectrum of the Li isotopes. It is found that the tensor force produces quite a characteristic effect on various states in each spectrum and those spectra are affected considerably by the tensor force. The energy difference between the spin-orbit partner, the p1/2 and p3/2 orbits of the last neutron, in 5Li is caused by opposite roles of the tensor correlation. In 6Li, the spin-triplet state in the LS coupling configuration is favored energetically by the tensor force in comparison with jj coupling shell model states. In 7,8,9Li, the low-lying states containing extra neutrons in the p3/2 orbit are favored energetically due to the large tensor contribution to allow the excitation from the 0s orbit to the p1/2 orbit by the tensor force. Those three nuclei show the jj coupling character in their ground states which is different from 6Li.