Surface Symmetry Energy of Nuclear Energy Density Functionals

TL;DR

This paper investigates the surface symmetry energy in nuclear energy density functionals, emphasizing its importance for modeling neutron-rich nuclei and implications for nuclear stability and r-process nucleosynthesis.

Contribution

It assesses the role of surface symmetry energy in nuclear deformation properties using Skyrme functionals and validates models against experimental data, highlighting the need for improved functionals.

Findings

Surface symmetry energy significantly influences neutron-rich nuclei deformation.

Experimental data on deformed nuclei are crucial for functional optimization.

Proper surface-symmetry energy determination impacts nuclear stability and r-process modeling.

Abstract

We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear energy density functionals. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface-symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron- rich matter and description of fission rates for r-process nucleosynthesis.