Vibrational relaxation in H2–CO and D2–CO mixtures, measured via stimulated Raman-ir fluorescence

Rate constants for vibration–vibration and vibration–translation energy transfers were measured by exciting the hydrogenic species in a stimulated Raman cavity and recording the subsequent rise and decay of ir fluorescence from the admixed CO at 4.7 μm. Under the justifiable assumption that the intraspecies redistribution of vibrational energy is very rapid, the time variation of fluorescence intensities and their dependence on the sample composition can be accounted for by the following processes: CO(v)+H2→CO+H2, kC,H=14.3±0.7 sec−1⋅torr−1; H2(v)+H2→H2+H2, kH,H=4.3±0.1; D2(v)+D2→D2+D2, kD,D=0.9±0.3; H2(v)+CO→H2+CO(v), kvH,C=4.5{+2.1−1.5; D2(v)+CO→D2+CO(v), kvD,C=138±25. The ratio (kvH,C/kvD,C) is surprisingly small in view of the near resonant condition for Δv (H2) =−1 coupled with Δv (CO) =+2.