Dissipation-fluctuation dynamics for fusion, deep-inelastic collisions, and heavy-ion induced fission with particle evaporation

Abstract

It is shown on selected examples how heavy-ion collisions (below 15 MeV/u) can be described by Langevin Monte Carlo dynamics. Fusion excitation functions, fusion spin distributions and Wilczynski diagrams of deep-inelastic collision (DIC) are calculated and compared with data. The bifurcation of fusion and DIC down to subbarrier energies is demonstrated. Time scales of DIC are obtained from calculating energy spectra of σ-electrons (atomic clock). By combining a (one-dimensional, overdamped) Langevin dynamics for the fission process with the statistical model (when the Kramers limit is reached after a transient time) we are not only able to calculate neutron multiplicities but also fission probabilities and (H.I.,xn) cross sections. Extending these investigations to a two-dimensional (elongation and neck) Langevin dynamics we obtain also kinetic energy distribution of fission fragments in coincidence with neutron multiplicities. By applying this model to a multi-dimensional decay rate for fission (derived with path integral methods) we calculate quantal corrections to the quasistationary Kramers result, which are not small even at temperatures reached in heavy-ion induced fission.