Anharmonic Effects in the Vibrational Relaxation of Diatomic Molecules in Expanding Flows

Time-dependent vibrational relaxation calculations are presented for anharmonic diatomic molecules in rapidly expanding flows. Specific calculations in CO-Ar mixtures predict highly distorted vibrational distributions as a result of anharmonic effects in the intramolecular exchange of vibrational energy. Further calculations are presented for N(2)-CO-Ar mixtures which demonstrate the effect on the vibrational distributions of the nonresonant transfer of vibrational energy between different anharmonic molecules. It appears possible to achieve high vibrational temperatures and hence useful small signal gains on partial inversions in upper vibrational levels.