Vibrational cooling of a highly excited anharmonic oscillator: Evidence for strong vibration–rotation coupling during relaxation

Abstract

The model of a diatomic molecule in a monoatomic solvent bath is considered to directly elucidate the role of vibration–rotation coupling for vibrational energy relaxation in liquids. Capacities of solute–solvent interactions as well as of Coriolis' and centrifugal forces are used as a means for displaying different energy exchange channels and manifesting the strength of vibration–rotation coupling. The ensemble averaged energy exchange between different degrees of freedom during specific solute vibrational phases is investigated. As an aside, we show that in the reduced density regime 0.5 to 0.75 the scaling of the frequency dependent frictional response with solvent density is practically the same for all effective vibrational frequencies explored by the anharmonic oscillator during energy relaxation.