Vibrational Relaxation of Diatomic Molecules in Gases and Liquids

When a diatomic molecule in a vibrationally excited state is placed in a host fluid it can lose a vibrational quantum by either radiative or nonradiative processes. In this article the rate of nonradiative vibrational transitions is expressed in terms of the rotational-kinetic-energy autocorrelation function. An interpolative approximation is made for the autocorrelation function and the vibrational relaxation time is computed. Good agreement with measurements of gaseous systems is obtained.