Theoretical study of different features of the fission process of excited nuclei in the framework of the modified statistical model and four-dimensional dynamical model

摘要

Evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity for the excited compound nuclei Yb-168, Yb-172, W-178 and Pa-227 produced in fusion reactions have been calculated in the framework of the modified statistical model and multidimensional dynamical model. In the dynamical calculations, the dynamics of fission of excited nuclei has been studied by solving three-and four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis, K, were considered in the four-dimensional dynamical model. A non-constant dissipation coefficient of K, gamma(k), was applied in the four-dimensional dynamical calculations. A comparison of the results of the three-and four-dimensional dynamical models with the experimental data showed that the results of the four-dimensional dynamical model for the evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity are in better agreement with the experimental data. It was also shown that the modified statistical model can reproduce the above-mentioned experimental data by choosing appropriate values of the temperature coefficient of the effective potential, lambda, and the scaling factor of the fission-barrier height, r(s).