Nuclear Level Density within Extended Superfluid Model with Collective State Enhancement

TL;DR

This paper enhances the superfluid model for nuclear level densities by incorporating collective state effects, providing tables and systematics for key parameters, and analyzing impacts on gamma-ray spectra and neutron reaction excitation functions.

Contribution

It introduces a modified superfluid model with collective state enhancement factors and provides systematic data and analysis tools for nuclear level density calculations.

Findings

Collective states significantly influence nuclear temperature calculations.

New tables for the asymptotic $a$-parameter and energy shifts are provided.

The model improves predictions of gamma-ray spectra and neutron reaction excitation functions.

Abstract

For nuclear level densities, a modification of an enhanced generalized superfluid model with different collective state enhancement factors is studied. An effect of collective states on forming the temperature is taken into account. The ready-to-use tables for the asymptotic value of $a$-parameter of level density as well as for addition shift to excitation energy are prepared using the chi-square fit of the theoretical values of neutron resonance spacing and cumulative number of low-energy levels to experimental values. The systematics of these parameters as a function of mass number and neutron excess are obtained. The collective state effect on gamma-ray spectra and excitation functions of neutron-induced nuclear reactions is investigated by the use of EMPIRE 3.1 code with modified enhanced generalized superfluid model for nuclear level density.