Level-density parameters in superheavy nuclei

TL;DR

This paper investigates the nuclear level densities of superheavy nuclei using advanced computational methods, analyzing their dependence on deformation, shell effects, and excitation energy to improve understanding of their stability.

Contribution

It introduces a systematic approach to calculate level-density parameters in superheavy nuclei, including nonaxial shapes and saddle points, and compares these with phenomenological models.

Findings

Level-density parameters vary significantly between ground states and saddle points.

The standard Fermi gas model requires modification for saddle point calculations.

The ratio of level-density parameters influences the survival probability of superheavy nuclei.

Abstract

We systematically study the nuclear level densities of superheavy nuclei, including odd systems, using the single-particle energies obtained with the Woods-Saxon potential diagonalization. Minimization over many deformation parameters for the global minima - ground states and the "imaginary water flow" technique on many deformation energy grids for the saddle points, including nonaxial shapes has been applied. The level density parameters are calculated by fitting the obtained results with the standard Fermi gas expression. The total potential energy and shell correction dependencies of the level-density parameter are analyzed and compared at the ground state and saddle point. These parameters are compared with the results of the phenomenological expression. As shown, this expression should be modified for the saddle points, especially for small excitation energy. The ratio of the level-density parameter at the saddle point to that at the ground state is shown to be crucial for the survival probability of the heavy nucleus.