Study of Pre-equilibrium Fission Based on Diffusion Model

In terms of numerical method of Smoluchowski equation thebehavior of fission process in diffusion model has been describedand analyzed, including the reliance upon time, as well as the deformationparameters at several nuclear temperatures in this paper. Thefission rates and the residual probabilities inside the saddlepoint are calculated for fissile nucleus n+²³⁸U reaction andun-fissile nucleus p+²⁰⁸Pb reaction. The results indicate that there really exists a transient fission process, which means that the pre-equilibrium fission should be taken into account forthe fissile nucleus at the high temperature. Oppositely, thepre-equilibrium fission could be neglected for the un-fissilenucleus. In the certain case the overshooting phenomenon of thefission rates will occur, which is mainly determined by the diffusivecurrent at the saddle point. The higher the temperature is, themore obvious the overshooting phenomenon is. However, the emissionsof the light particles accompanying the diffusion process mayweaken or vanish the overshooting phenomenon.