Existence of the bottleneck in vibrational relaxation of diatomic molecules

High-temperature vibrational relaxation of diatomic molecules is analyzed using master equation and Fokker-Planck diffusion equation modeling. Both approaches me based on the nonperturbative forced harmonic oscillator vibrational energy transfer rate model. The results show that the effect of the retarded diffusion at the intermediate vibrational energies during the relaxation process (bottleneck), predicted in the previous studies, does not exist at the high temperatures. It is also shown that the interpretation of the high-temperature vibrational relaxation as a diffusion-type process is inadequate because of the strong effect of multiquantum energy transfer. The obtained results, applied to interpretation of the rates of thermal dissociation, suggest an important role of rotations in molecular activation at the high vibrational energies.