Possibilities to verify the level density and radiative strength functions, extracted from the two-step gamma-cascade intensities

TL;DR

This paper discusses methods to verify level density and radiative strength functions in nuclei, which are difficult to measure directly, by fitting models to gamma-ray spectra and analyzing the structure of excited nuclear levels.

Contribution

It introduces a verification approach for nuclear parameters using total gamma-spectra calculations and explores their dependence on excitation energy and nuclear structure.

Findings

Calculation of gamma-spectra helps verify nuclear parameters.

Radiative strength functions likely depend on neutron-binding energy.

Level density and strength functions may vary with nuclear resonance structure.

Abstract

The direct determination of the excitation level density and radiative strength functions of their exciting gamma-transitions is impossible for the larger part of the stable and long-life radioactive target nuclei. This circumstance is uniquely determined by the fact, that the level spacing much less than the resolution of the existing spectrometers of gamma-rays and charged particles. The extraction of these parameters of nucleus in this situation can be executed by their only fitting to the most probable values, reproducing the measured in the nuclear reactions spectra and sections. This inverse problem of mathematical analysis of its nature is principally ambiguous. Moreover, system of equations, those connecting the number of excitable levels and probability of the emission of charge particles are assigned usually within the framework of some assumptions about the mechanism of nuclear reaction and factors, determining the dynamics of the studied process. The verification of these parameters can be partially executed by the calculation of total gamma-spectra for their different sets. As, in particular, the results of this analysis show, the calculation of the structure of the excited levels to a change in the form of the energy dependence of radiative strength functions most likely must be considered to the neutron-binding energy. It is not possible to exclude the possibility of that, that also radiative, and neutron strength functions depend on the structure of neutron resonance and for the higher excitation energies.