Margitych T. Distribution of fusion fragments of highly excited nuclei by mass and kinetic energy

The results of theoretical calculations of the mass-energy distributions of the fission process of highly excited atomic nuclei with the mass numbers A< 220 are present in this thesis. New models for calculating mass and kinetic energy distributions of fission fragments for nuclear with A< 220 in reactions a + 197Au-> fission and a + 165Ho->fission reactions have been developed. The nuclear-nuclear interaction potential of highly deformed nuclei for symmetric and asymmetric systems is also calculated. Various parametrizations of the nuclear part of the interaction potential are also taking into account to estimate the mass yields of fission fragments for reaction a + 197Au-> fission. The results significantly clarify the physical interpretation and improve the accuracy of the description of the induced fission of highly excited atomic nuclei with A<220 . These studies are related to the modern nuclear physics directions. The models proposed in this thesis can be used to predict and describe of experimentally obtained mass-energy distributions of induced fission fragments induced by various particles and gamma rays. The full nuclei interaction consists of the deformation energy of nuclear surfaces, rotation energy, the components of Coulomb and nuclear interactions. The minimum values of the interaction barriers heights for nuclei systems considered in this work are estimated. It was found that the minimum value of the nuclear-nuclear interaction potential is observed in the axially symmetric nuclei with the quadrupole, octupole, and hexadecapole deformation parameters of nuclear surfaces. It has been established that the quadrupole deformation of the nuclear surfaces has the principal influence on the minimum value of the interaction barrier height; the contributions of the octupole and hexadecapole deformations are smaller. The lowest values of the barrier heights for different fragments determine the position of the two-body saddle points. These points are used to calculate the mass and kinetic energy distributions of fission fragments of highly excited nuclei in our models. It was shown that the distribution of the fragments of binary fission of highly excited nuclei with A<220 is formed in a two-body saddle point. The value of two-body saddle point is different for different fragment pairs. The positions of the two-body saddle point, which is located on the potential energy surface at small distances between the deformed nuclei surfaces, are found. It is shown that the height of this two-body saddle point for nuclei with A<220 is larger than the height of "one-body" barrier fission in the fissioning nuclei. It was established that the number levels of the system of two interacting fission fragments in the two-body saddle point are related to the yield probability of the corresponding fragments pair. The model for description of the mass yields and kinetic energy distributions of fission fragments of highly excited nuclei with A<220 are developed. In these methods were taken into account the nucleus-nucleus interaction in the output channels, in particular, the barrier between two separated fragments that called «two-body» saddle point. The mass yields of fission fragments of highly excited nuclei with the number of nucleons with A<220 without any new additional parameters are described in the framework of the model. The trajectory equation of the fragments motion is used in the framework of the developed model. The energy dissipation and statistical fluctuations were taken into account in the consideration. Using this method a good description of the mass and kinetic energy distributions of fission fragments of highly excited nuclei with A<220 were obtained.