ABSTRACT
The behavior of the system in the kinetic process is determined by the dependence of its density matrix p on time. For non-adiabatic transitions the perturbations Hkm are small and in solving the set of Equations it is usually sufficient to use first-order perturbation theory. The method of the density matrix enables to consider more complicated situations, in particular, to investigate non-Condon effects and deviations from the Born-Oppenheimer approximation. In particular, they include the fluctuation preparation of the potential barrier and the inertial effect. Note that the model of harmonic oscillations enables to take into account in an exact manner a number of effects, which are due to the interrelation of the motion of individual atoms, which in other models requires certain approximations. The method of the density matrix enables to consider more complicated situations, in particular, to investigate non-Condon effects and deviations from the Born-Oppenheimer approximation.
