Systematics and possible nonstatistical behaviour of (n,2n) cross sections

A systematical analysis of experimental (n, 2n) cross sections has been carried out by many authors for long time. However, a substantiated theoretical approach to explain the observed systematical regularity of the experimental (n, 2n) cross sections has not been available until now. In this work, in the framework of the statistical model, a general expression for (n, 2n) reaction cross sections is obtained using the compound mechanism and evaporation model. This expression is then used to deduce the nonstatistical share of the (n, 2n) cross section. It is shown for the first time that the nonstatistical theoretical formula adequately describes the experimental (n, 2n) cross section data for 14–15 MeV neutrons taken from the EXFOR library.