Experimental Evidence of Large Collective Enhancement of Nuclear Level Density and its Significance in Radiative Neutron Capture

TL;DR

This paper presents experimental evidence of a significant collective enhancement in nuclear level density for deformed $^{171}$Yb, revealing its impact on neutron capture processes relevant to astrophysics.

Contribution

It provides the first experimental measurement of a large collective enhancement factor of 40 in nuclear level density, confirming microscopic model predictions and highlighting its astrophysical importance.

Findings

Large collective enhancement factor of 40±3 measured

Enhanced understanding of energy-dependent nuclear level density

Implications for radiative neutron capture cross sections

Abstract

The collective enhancement of nuclear level density and its fade out with excitation energy in deformed $^{171}$Yb nucleus has been inferred through an exclusive measurement of neutron spectra.The statistical model analysis of neutron spectra demonstrated a large collective enhancement factor of 40$\pm$3 for the first time, which corroborates with the recent microscopic model predictions but is an anomalous result compared with the measurements in the nearby deformed nuclei. The complete picture of the energy dependent collective enhancement has been obtained by combining with Oslo data below neutron binding energy. The significance of large collective enhancement in radiative neutron capture cross section of astrophysical interest is highlighted.