Calculation of fission fragment characteristics for the reactions n $$_\mathrm{th}+^{235}$$ th + 235 U and n $$_\mathrm{14\; MeV}+^{235}$$ 14 MeV + 235 U

A model for a description of various fission fragment characteristics is proposed. The both nascent fission fragments consist of either the single-body or the two-body systems. The one-body fragment is a single nucleus, while the two-body fragment is the nucleus interacting with the $$\alpha $$ -particle. The $$\alpha $$ -particle have its origin to the neck nucleons. The yield of fission fragments in the model is linked to the number of states over the barrier of the saddle point, which is between the contacting and well-separated fission fragments. The crucial role of the three-body (nucleus- $$\alpha $$ -nucleus) systems at a passing through the saddle point is shown. After passing the saddle point, the $$\alpha $$ -particle is fusing with the nearest nucleus and forming the final fragment, because the distance between the nucleus and $$\alpha $$ -particle is smaller the barrier distance of the $$\alpha $$ -nucleus potential. As a result, the binary fission is realized in the framework of the model. If the $$\alpha $$ -particle is not fusing with the any fragment than the ternary fission occurs. The mass dependencies of the fragments yield, the kinetic energy and neutron emission number emitted by fragment calculated in the model agree well with available experimental data for binary fission of $$^{235}$$ U by thermal and 14 MeV neutrons. The root mean deviation between theoretical and experimental values of the decimal logarithm of nuclide yields for the fission of $$^{235}$$ U by thermal and 14 MeV neutrons are 0.756 and 1.02, respectively. The values of the ground-state quadrupole deformation of neutron-rich nuclei related to the fragments are estimated.