Photoneutron reactions on gold in the giant dipole resonance region: reaction cross sections and average kinetic energies of $(\gamma,\,xn)$ photoneutrons

TL;DR

This study provides new measurements of photoneutron reaction cross sections and neutron energies for gold in the giant dipole resonance region, challenging previous cross section adjustments and comparing results with models.

Contribution

It offers new experimental data on $^{197}$Au photoneutron reactions and refines the understanding of giant dipole resonance parameters in this energy region.

Findings

Photoabsorption cross sections agree with Saclay results.

No support for lowering Saclay cross sections by 8%.

Observed non-statistical high-energy neutron emission.

Abstract

In this work, we present new data on the $^{197}$Au photoneutron reactions in and above the giant dipole resonance region, obtained by using 8 to 39~MeV quasi-monochromatic $\gamma$-ray beams produced at the NewSUBARU facility in Japan and a high-and-flat efficiency neutron detection system. We report absolute cross sections and mean photoneutron energies for the $^{197}$Au$(\gamma,\,inX)$ reactions with $i$~=~1 to 4. The photoabsorption cross section was obtained as the sum of the $(\gamma,\,inX)$ reaction cross sections. The giant dipole resonance parameter values were obtained by fitting the experimental photoabsorption cross sections. The present photoabsorption cross sections are in good agreement with the Saclay results of Veyssiere~\emph{et al.}. Thus, our study does not support the recommendation of Berman~\emph{et al.} of lowering the Saclay photoabsorption cross sections by 8$\%$. We observed a non-statistical high-energy neutron emission in the $(\gamma,\,n)$ reaction in the low-energy region between $S_n$ and 10~MeV. The present results are compared with data from the literature and statistical model calculations performed with the TALYS and EMPIRE codes.