Effect of excitation of a fissile nucleus on fission energy distribution between internal and collective motions

The energy dependences of the average kinetic energy of fission fragments, anti Esub(k), and the average number of prompt neutrons, anti νsub(p), is considered for neutron-induced fission of 232Th in the energy range 1.2-2.5 MeV. The behaviour of anti Esub(k) and anti ν sub(p) indicate a redistribution of the fission energy between collective and internal motions depending on excitation of the fissile nucleus. Arguments are proposed to explain a difference between the behaviour of anti Esub(k) and anti νsub(p) for 232Th and that for other fissile heavy nuclei. The explanation is based upon a change of the role of shell effects at different levels of the nuclear excitation at the stage of evolution of the fissile nucleus from the saddle point to the scission