Shell-model study of quadrupole collectivity in light tin isotopes

TL;DR

This study uses a realistic shell-model approach with perturbation theory to analyze quadrupole collectivity in light tin isotopes, emphasizing the importance of cross-shell excitations and neutron effective charges.

Contribution

It introduces a novel double-step method to reduce model space complexity and provides a detailed theoretical description of quadrupole collectivity in light tin isotopes.

Findings

Cross-shell excitations are crucial for accurate modeling.

Neutron effective charges are larger than standard empirical values.

The model successfully reproduces observed B(E2) transition strengths.

Abstract

A realistic shell-model study is performed for neutron-deficient tin isotopes up to mass A=108. All shell-model ingredients, namely two-body matrix elements, single-particle energies, and effective charges for electric quadrupole transition operators, have been calculated by way of the many-body perturbation theory, starting from a low-momentum interaction derived from the high-precision CD-Bonn free nucleon-nucleon potential. The focus has been put on the enhanced quadrupole collectivity of these nuclei, which is testified by the observed large B(E2;0+ -> 2+)s. Our results evidence the crucial role played by the Z=50 cross-shell excitations that need to be taken into account explicitly to obtain a satisfactory theoretical description of light tin isotopes. We find also that a relevant contribution comes from the calculated neutron effective charges, whose magnitudes exceed the standard empirical values. An original double-step procedure has been introduced to reduce effectively the model space in order to overcome the computational problem.