Systematics of the average neutron yield in heavy-ion-induced fission

A simple empirical description is proposed for the behavior of the total neutron yield bar νt, in heavy-ion-induced fission and also for that of the components of this yield corresponding to prefission neutrons (bar νpre) and postfission neutrons (bar νpost) (emitted, respectively, before and after the rupture) as a function of the excitation energy E* and the mass number A of the initial fissioning nuclei. The dependence of the neutron yields on the energy Ei and the mass Ai of the bombarding particles is discussed. The dependence causes difficulty in an attempt to combine the experimental data on fission induced by heavy ions with the data on fission induced by light particles (Ai much-lt 4) in the actinide region. This difficulty is discussed. 44 refs., 7 figs