Semiclassical three-dimensional model for vibrational relaxation

In a semiclassical three-dimensional treatment of the atom-diatom scattering problem, we have included the intermultiplet transitions to infinite order, whereas simultaneous rotational and vibrational transitions are treated to first order. Thus we have found criteria for neglect of intermultiplet transitions. With this model we have investigated three systems, namely, the He–H2, the Ar–HCl, and the Ar–O2 systems. We found that transitions with change in both vibrational and rotational quantum number were dominant for the vibrational relaxation process in the Ar–HCl case, while they were important for the Ar–O2 system and negligible for the He–H2 system.