Nuclear scission and fission-fragment kinetic-energy distribution: Study within three-dimensional Langevin dynamics

A multi-dimensional stochastic approach based on three-dimensional Langevin equations is applied for calculation of the first four moments of the kinetic-energy distribution of fission fragments in a wide range of Coulomb parameter 700<Z2/A1/3<1700. A modified one-body mechanism of nuclear dissipation with reduction factor ks=0.25 and different scission criteria widely used in modern fission theory are applied: zero-neck-radius RN=0 and finite-neck-radius RN=0.3R0. A probabilistic scission criterion has been proposed also for the description of the scission process of compound nucleus. All of these scission criteria result in a good description of experimental data of the first moment of the kinetic-energy distribution. At the same time all the scission criteria provide satisfactory description of the second, third and fourth moments of the energy distribution. On the basis of theoretical calculations we cannot discriminate scission criterion, which scission criterion gives the best agreement with the experimental data. A possible way to improve the theoretical description of the experimental data could be introduction of additional collective coordinates, which could provide more flexible shapes of compound nucleus during the descent from saddle to scission.