Kinetic equations for a dynamical system in a condensed medium and a strong external field

Kinetic equations are obtained for the parameters of a quantum dynamical system interacting with structural groups of a condensed medium, which acts as a thermal reservoir. The equations are valid for arbitrary strength of an external (constant and variable) field that acts only on the dynamical system. Approximate kinetic equations valid in the presence of a highfrequency external field are obtained for specific dynamical systems – a two-level system and a quantum rotator. For these same dynamical systems and representation of the medium (thermal reservoir) by a set of harmonic oscillators, the relaxation times of the dynamical system are obtained as functions of the amplitude and frequency of the external field, and also the temperature.