V-V and V-T/R energy transfer studies of C2H4 by infrared laser double resonance

Multiple exponential decay of the ν7, ν = 1 state of ethylene has been observed using laser double resonance. The slower measured rate is in excellent agreement with the results of fluorescence experiments and is consistent with a mechanism involving vibration-translation/rotation energy transfer in C2H4. The fast measured rate appears to arise from equilibration of the ν7, ν = 1 state with nearby excited vibrational states. Large differences in rates have been observed for this fast process during C2H4–C2H4 collisions versus C2H4-rare gas collisions. The temperature dependence of the slow decay rate has been measured in ethylene-rare gas mixtures and the deactivation probabilities found to be in general agreement with predictions based on Landau-Teller theory.