Parameters of Distribution of the Primary Gamma-Transition Intensities Following Resonance Neutron Capture and Some Properties of Compound Nuclei $^{157,159}$Gd

TL;DR

This paper re-analyzes experimental data on primary gamma-transition intensities in Gd isotopes, revealing step-like structures in level density and significant changes in nuclear structure above 1.0-1.5 MeV.

Contribution

It provides new detailed statistical analysis of gamma-transition intensities and strength functions, highlighting structural changes in nuclei at specific excitation energies.

Findings

Confirmation of step-like structure in level density below 3 MeV.

Observation of changes in radiative strength functions with excitation energy.

Detection of significant variations in transition ratios indicating structural shifts.

Abstract

The re-analysis of the published experimental data on the primary gamma-transition intensities following neutron capture in different groups of neutron resonances in $^{156,158}$Gd has been performed. There are determined the most probable values of sum of E1 and M1 primary transitions, numbers of excited by them levels of both parities, ratios of radiative strength functions k(M1)/k(E1), dispersions of deviations of random values of intensities from the average and ratios of mean intensities of primary transitions to levels J=5/2 with respect to analogous data for J=1/2 and 3/2 (capture of the 24 keV neutrons) in narrow excitation energy intervals. All the data on level density and sums of radiative strength functions confirm the presence of clearly expressed step-like structure in level density below 3 MeV and general trend in change in strength functions as changing primary gamma-transition energy. Variations of distribution dispersions and, especially, ratio k(M1)/k(E1) (or $k(E1)/k(M1)$) at changing excitation energy point to strong change in structure of these nuclei above 1.0-1.5 MeV.