Integrated preequilibrium-cum-statistical model approach for the (n, 2n) cross sections around 14.5 MeV

The absolute values of ($n, 2n$) reaction cross sections around 14.5 MeV are calculated using an integrated preequilibrium-cum- statistical model. The absolute preequilibrium fraction is calculated using the Griffin-Williams exciton model as used by Braga-Marcazzan et al. in the analysis of ($n, p$) cross sections around 14 MeV. The reduction of flux for the statistical component due to the preequilibrium process has been accounted for by including both neutron and proton emission. This calculation, which is global and free from any new parameter, improves the agreement between theory and experiment reducing the 0.87 rms deviation of the statistical model to 0.48 for 88 nuclei in the mass range $60<A<\mathrm{}209\mathrm{}$. For nuclei with $A<\mathrm{}60\mathrm{}$ there is not much improvement.