Mode-to-mode energy transfer in collisions between S1 state aniline and Ar, CO, CO2, C2H2, C3H4, OCS, Xe, and N2O

Abstract

SVL fluorescence spectroscopy was used to study V‐T,R processes in collisions of 0⁰ aniline with Ar, Xe, CO, CO₂, OCS, N₂O, acetylene, and allene. Populations were monitored in eight aniline vibronic levels. To first order, the experimental propensity rules for single‐collision up pumping of 0⁰ aniline to these levels are identical for all collision gases. An exception is the unusually large rate constant for population of the 1¹ level in collisions with allene, whose 11₁ level is nearly degenerate with the I¹ level in aniline; this may be evidence of an important V–V process. The endoergic up‐pumping probabilities correlate well with μ^1/2 for rare gas partners, but poorly for the other collision gases. No evidence is found that V‐R processes contribute substantially to the rate constants for aniline in collision with CO or the polyatomic gases. The quantitative propensity rules provide a basis for a mode‐to‐mode collisional energy transfer theory, developed by Freed, in which the observed large V‐T,R cross sections arise as a direct consequence of the intramolecular intermode coupling within large molecules such as aniline.