Collisional deactivation of laser-excited acetylene by H2, HBr, N2 and CO

Abstract

The deactivation of vibrationally excited acetylene by collisions with H₂, HBr, N₂ and CO was studied using the laser-induced fluorescence technique. After excitation of the coupled modes ν₃ and (ν₂+ν₄+ν₅) of C₂H₂ at 3300 cm^–1 the time dependence of the fluorescence signals from ν₂(1974 cm^–1) and ν₅(729 cm^–1) was investigated. The rate constants for the deactivation of ν₂ and ν₅ by the collision partners CO and N₂ were found to be relatively low and comparable with the known corresponding rate constants for rare-gas collisions. On the other hand the measured rate constants for the deactivation ν₂ and ν₅ by collisions with H₂ and HBr are much higher. Additional measurements of CO fluorescence near 4.7 µm showed that the activation and deactivation of CO (v= 1) by collision with C₂H₂ is very effective. The influence of the measured rates on the C₂H₂ laser is considered briefly.