Two-phonon relaxation of a classical oscillator interacting with a condensed medium

Energetic transitions between vibrational levels of an anharmonic oscillator interacting with condensed medium are studied by means of the method of nonequilibrium density matrix for a quantum subsystem. Kinetic equations describing one- and twoquantum transitions in the oscillator are derived. Inner conversion time constants which determine the establishing of equilibrium state are calculated in the classical high temperature limit.