Radial and Tangential Friction Coefficients: Derivation of Formulas, Calculation and Application in Simulation of the Collision Process of a Spherical Projectile Nucleus With a Deformed Target Nucleus

The issue of accounting for radial and tangential friction in the entrance channel of the nuclear reactions S+U and Ni+U, occurring with an impact parameter not equal to zero, is considered. Reaction are simulated in the approximation of the frozen deformation degrees of freedom of the colliding nuclei. The shape of the target nucleus is elongated, the symmetry axis of the target nucleus is oriented arbitrarily in a plane drawn through the vector of the initial momentum of the projectile nucleus and the center of mass of the target nucleus. The shape of the projectile nucleus remains spherical throughout the entire collision process of the initial nuclei. The paper considers the dynamic evolution of two degrees of freedom of a system, namely, a parameter describing the distance between the centers of mass of colliding nuclei and a parameter describing the orientation of the target nucleus. It is shown that consideration of tangential friction between colliding nuclei makes it possible to get rid of the overestimation of the probability of capture of a projectile nucleus by a target nucleus at high angular momenta. The simulation results are compared with experimental data and with the results of calculations performed in the previous version of the model.