Influence of the symmetry energy on the nuclear binding energies and the neutron drip line position

TL;DR

This study investigates how the symmetry energy influences nuclear binding energies and the neutron drip line, revealing that stiffer symmetry energies predict more bound nuclei and establishing a correlation between symmetry energy and nuclear stability.

Contribution

The paper introduces a systematic analysis of the impact of symmetry energy on nuclear binding and drip lines using relativistic energy density functionals constrained at saturation density.

Findings

Stiffer symmetry energies predict more bound nuclei near the neutron drip line.

A correlation exists between the number of bound nuclei and the symmetry energy.

The relationship varies depending on the nuclear density considered.

Abstract

A clear connection can be established between properties of nuclear matter and finite-nuclei observables, such as the correlation between the slope of the symmetry energy and dipole polarizability, or between compressibility and the isoscalar monopole giant resonance excitation energy. Establishing a connection between realistic atomic nuclei and an idealized infinite nuclear matter leads to a better understanding of underlying physical mechanisms that govern nuclear dynamics. In this work, we aim to study the dependence of the binding energies and related quantities (e.g. location of drip lines, the total number of bound even-even nuclei) on the symmetry energy $S_2(\rho)$. The properties of finite nuclei are calculated by employing the relativistic Hartree-Bogoliubov (RHB) model, assuming even-even axial and reflection symmetric nuclei. Calculations are performed by employing two families of relativistic energy density functionals (EDFs), based on different effective Lagrangians, constrained to a specific symmetry energy at saturation density $J$ within the interval of $30$--$36$ MeV. Nuclear binding energies and related quantities of bound nuclei are calculated between $8 \leq Z \leq 104$ from the two-proton to the two-neutron drip line. As the neutron drip line is approached, the interactions with stiffer $J$ tend to predict more bound nuclei, resulting in a systematic shift of the two-neutron drip line towards more neutron-rich nuclei. Consequentially, a correlation between the number of bound nuclei $N_{nucl}$ and $S_2(\rho)$ is established for a set of functionals constrained using the similar optimization procedures. The direction of the relationship between the number of bound nuclei and symmetry energy highly depends on the density under consideration.