Isomeric cross section of theAu197(n,2n) reaction

Abstract

In the present work, the $^{197}\mathrm{Au}$($n,2n$) reaction cross section is experimentally determined relative to the $^{27}\mathrm{Al}$($n,\ensuremath{\alpha}$)$^{24}\mathrm{Na}$ reaction at incident neutron energies of 9.0--10.5 MeV by means of the activation technique. The quasimonoenergetic fast neutron beam was produced via the $^{2}\mathrm{H}$($d,n$)$^{3}\mathrm{He}$ reaction at the 5.5-MV Tandem Van de Graaff accelerator at the National Centre of Scientific Research (NCSR) ``Demokritos'' and was studied to determine the contribution of background ``parasitic'' neutrons using the multiple foil activation technique and the SULSA unfolding code. The cross sections for the population of the second isomeric state (${12}^{\ensuremath{-}}$) of $^{196}\mathrm{Au}$ and the sum of the ground (${2}^{\ensuremath{-}}$) and first isomeric state (${5}^{\ensuremath{-}}$) population cross sections were independently determined. Auxiliary Monte Carlo simulations were performed with the MCNP code. Theoretical calculations of the above cross sections in the 8--25 MeV region were carried out with the use of the STAPRE-F, EMPIRE, and TALYS codes, which were also compared in their implementation of the generalized superfluid model. The theoretical results are compared with previous work in the same mass region, and the strong dependence on the level scheme of the nuclei involved was revealed.