A dynamical interpretation of fusion-fission reactions using four-dimensional Langevin equations

摘要

Four-dimensional Langevin equations have been applied to calculate the neutron multiplicity and evaporation residue cross section for hot nuclei. The projection of the total spin of the compound nucleus to the symmetry axis, K, is the fourth dimension in Langevin dynamical calculations. The relaxation time of the K as a function of the dynamical parameters is investigated. Calculations were performed for the ~(18)O+~(192)Os and ~(19)F+ ~(169)Tm reactions with a non-constant dissipation coefficient for the K coordinate. The obtained results based on four-dimensional Langevin equations with a non-constant dissipation coefficient in comparison with calculations based on a constant dissipation coefficient (γ_K = 0.077(MeVzs)~(-1/2)) are in better agreement with the experimental data. The difference between the two models for the evaporation residue cross section is high, whereas for neutron multiplicity, the discrepancy is low.