Vibrational-translational relaxation harmonic oscillators

Note added in proof In view of the failure of the harmonic oscillator model to account for the observed rate of activation in unimolecular dissociation reactions (the dissociation lag problem) these calculations have been repeated for a Morse anharmonic oscillator with transition between nearest and next-nearest neighbor levels [S. K. Kim, /. Chem. Phys. (to be published)]. The numerical evaluation of the analytical results obtained by Kim has not yet been carried out. From the results obtained by us and our co-workers [Barley, Montroll, Rubin, and Shuler, /. Chem. Phys. in press)] on the relaxation of vibrational nonequilibrium distributions of a system of Morse anharmonic oscillators it seems clear, however, that the anharmonic oscillator model with weak interactions (i.e., adiabatic perturbation type matrix elements) does not constitute much of an improvement on the harmonic oscillator model in giving the observed rates of activation. The answer to tliis problem would seem to lie in a recalculation of the collisional matrix elements for translational-vibrational energy exchange which takes account of the strong interactions in highly energetic collisions which can lead to direct dissociation. 

This example is one of the many relaxation processes attributed to the col-lisional vibrational-translational energy exchange. Without discussing other processes, we shall only mention those most important for the kinetics of nonequilibrium reactions vibrational relaxation of anharmonic oscillators in a heat bath, relaxation of one- and two-component mixture of harmonic oscillators with resonant and quasi-resonant energy exchange and relaxation of anharmonic oscillators [87, 164, 343, 460] (see Section IV. 15). 

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