Radial and Tangential Friction Coefficients: Derivation of Formulas, Calculation and Application in Modeling of the Heavy Ion Collision Process

A method for calculating the forces and moments of friction forces arising between two colliding nuclei with a nonzero impact parameter is considered. At this stage of the work, it is assumed that colliding nuclei remain spherical throughout the entire collision process. The collision process of spherical atomic nuclei is simulated taking into account their gradual inclusion in rotation around their own axes. It is shown that it takes time about \(10^{-21}\) s from the moment of the transition of the system through the Coulomb barrier to the stop of the relative rotation of colliding nuclei. It is proposed to consider the stopping of radial motion and relative rotation of colliding nuclei as conditions for capturing the projectile nucleus by the target nucleus. That is, at the moment of capture, the system should behave like a rigid rotating dumbbell. Comparison of the calculation results of the capture cross sections with the experimental data shows a good predictive power of the considered approximate model in the case of a strongly asymmetric reaction of \({}^{16}\textrm{O}+{}^{208}\) Pb (for all reaction energies) and in the case of high-energy reactions of \({}^{36}\textrm{S}+{}^{208}\) Pb and \({}^{40}\textrm{Ca}+{}{208}\) Pb.