Fission dynamics in systems of intermediate fissility

Abstract

It is well accepted that fission is a slow process dominated by nuclear viscosity. This is demonstrated by experimental observations, mainly based on measurements of fission fragment TKE, pre-scission light particles and GDR γ-ray multiplicities, energy spectra. The fission time-scale, as well as the nature of energy dissipation during the process and its dependence on the nuclear shape and temperature are the main aspects which have often been addressed. In spite of the extensive work, there are still many open questions on the dynamics of the fission process, mainly due to the lack of constraints on the models and to the different probes used. Intermediate fissily systems are particularly suited for this study as they present comparable cross sections in the fusion-fission and fusion-evaporation channels, allowing to measure observables in both channels, and therefore to further constrain the models. Furthermore, the path from equilibrium to saddle configuration is expected to dominate with respect to saddle-to-scission one, reducing the complexity of the physical process to be studied. We present here an in depth review of a study performed on the nucleus 132Ce, which shows the limits of the statistical model in accounting for an extended set of observables. We further present the analysis of the same data with a 3D Langevin dynamical approach which proves to be capable of reproducing the values of the whole set of observables. Our analysis reinforce the fact that extended data sets are essential to achieve reliable simulations to address the open questions on fission dynamics and strongly suggest the use of setups of high efficiency.