Theory of collisional equilibration of a radiatively excited molecular gas

A theory for the statistical equilibration of the degenerate vibrational modes of a polyatomic molecule is presented. It is shown how combined radiative and bimolecular collisional development of the degenerate multimode system may be related to that of the single-mode system. Exact multimode rate equations are derived and used to demonstrate that for the ideal harmonic system only transient disturbances of quasithermal equilibrium are permitted. A model theory for the truncated harmonic system in terms of rate equations for the first and second population distribution moments is studied. A solution is presented and related to recent experimental studies of cyclobutanone.