Effect of fission dynamics on the spectra and multiplicities of prompt fission neutrons

With the goal of examining their effect on the spectra and multiplicities of the prompt neutrons emitted in fission, the authors discuss recent advances in a unified macroscopic-microscopic description of a large-amplitude collective nuclear dynamics. The conversion of collective energy into a single-particle excitation energy is calculated for a new surface-plus-window dissipation mechanism. By solving equations of motion for initial conditions appropriate to fission, the authors obtain the average fission-fragment translational kinetic energy and excitation energy. The spectra and multiplicities of the emitted neutrons, which depend critically upon the average excitation energy, are then calculated on the basis of standard nuclear evaporation theory, taking into account the average motion of the fission fragments, the distribution of fission-fragment residual nuclear temperature, the energy dependence of the cross section for the inverse process of compound-nucleus formation, and the possibility of multiple-chance fission. Some illustrative comparisons of the authors' calculations with experimental data are shown