A Systematics to Investigate the (n,) Cross Section with Energy Below 20 MeV Based on the Evaporation and Exciton Models

To simplify the calculation, some assumptions are considered in the current work. The preequilibrium emission in the first step in the equilibrium process, which is characterized by exciton n = 3 and "never come back," is considered in the preequilibrium emission process; the alpha emission is only completed with the neutron and proton emission, and the second particle emission is neglected. Under those assumptions, a semiempirical systematics of the cross section for the (n,) reaction is obtained on the basis of the evaporation and exciton models for the energies ranging up to 20 MeV. Within the nuclide mass region of 23 A 209, a strong dependence on (N - Z + 1)/A and the incident neutron has been observed. The predictions of the semiempirical systematics with the global parameter of the excitation functions for the (n,) reaction are in good agreement with the experimental data.