Multiple collision effects in the vibrational relaxation of molecules in the liquid phase

Vibrational relaxation in fluids is examined using a simple stochastic model of a relaxing oscillator. As an example of multiple collision effects, the coupling between translational and relative motion which occurs for an asymmetric oscillator in a viscous fluid is investigated. A semiclassical calculation of the relaxation constant in this model suggests that for some molecules this effect may be important in the liquid phase.