Determination of the nuclear level densities and radiative strength function for 43 nuclei in the mass interval 28≤A≤200

David Knezevic,Ludmila V Mitsyna,Anatoly M Sukhovoj,Stephan Oberstedt,Nikola Jovancevic,Vu D Cong,Franz-Josef Hambsch,Zsolt Revay,Christian Stieghorst,Aleksandar Dragic,Miodrag Krmar,F.-J Hambsch,I Ruskov,N Carjan

doi:10.1051/epjconf/201816900007

Abstract

The determination of nuclear level densities and radiative strength functions is one of the most important tasks in low-energy nuclear physics. Accurate experimental values of these parameters are critical for the study of the fundamental properties of nuclear structure. The step-like structure in the dependence of the level densities p on the excitation energy of nuclei Eex is observed in the two-step gamma cascade measurements for nuclei in the 28 ≤ A ≤ 200 mass region. This characteristic structure can be explained only if a co-existence of quasi-particles and phonons, as well as their interaction in a nucleus, are taken into account in the process of gamma-decay. Here we present a new improvement to the Dubna practical model for the determination of nuclear level densities and radiative strength functions. The new practical model guarantees a good description of the available intensities of the two step gamma cascades, comparable to the experimental data accuracy.

Highlights

The development of theoretical models of nuclear structures requires a set of experimental information of the excited levels density, ρ, and of the values of the partial width, Γ, of all possible decay channels
The step-like structure in the dependence of the level densities ρ on the excitation energy of nuclei Eex is observed in the two-step gamma cascade measurements for nuclei in the 28 ≤ A ≤ 200 mass region
Based on the experimental data collected by two-step gamma cascades experiment a model for description the gamma-decay of neutron resonance was developed at JINR, Dubna [2, 3]

Summary

Introduction

The development of theoretical models of nuclear structures requires a set of experimental information of the excited levels density, ρ, (with given quantum numbers) and of the values of the partial width (radiative strength function), Γ, of all possible decay channels. Based on the experimental data collected by two-step gamma cascades experiment a model for description the gamma-decay of neutron resonance was developed at JINR, Dubna [2, 3] In this model the level density ρ of quasi-particles in any nucleus is defined using the known model of nquasi-particle levels. The experimental results of two step gamma cascades intensity for 43 nuclei in the 28 ≤ A ≤ 200 mass region were fitting by this model This provide us possibility to extract parameters of nuclear structure such as breaking thresholds of the second and the third Cooper pairs, ratio of the collective level density to the total one or level parity

Dubna two-step gamma cascades method

Model of the gamma-decay of neutron resonance

Results and discussion

Conclusion