Measurement of the damping of nuclear shell effect in the doubly magic $^{208}$Pb region

TL;DR

This study measures how the nuclear shell effect diminishes with excitation energy near doubly magic $^{208}$Pb, providing quantitative damping parameters through neutron spectra analysis.

Contribution

First quantitative extraction of damping parameter and level density parameter for nuclei near $^{208}$Pb using neutron spectra from transfer reactions.

Findings

Large shell correction energy near $^{208}$Pb

Small shell correction energy for $^{184}$W

Quantitative damping parameters obtained

Abstract

The damping of the nuclear shell effect with excitation energy has been measured through an analysis of the neutron spectra following the triton transfer in the $^7$Li induced reaction on $^{205}$Tl. The measured neutron spectra demonstrate the expected large shell correction energy for the nuclei in the vicinity of doubly magic $^{208}$Pb and a small value for $^{184}$W. A quantitative extraction of the allowed values of the damping parameter $\gamma$, along with those for the asymptotic nuclear level density parameter $\tilde{a}$, has been made for the first time.