Abstract

Collision-induced V-V energy transfer between different vibrational modes of a small polyatomic molecule in the gas phase generally occurs on the time scale of 10¹–10³ gas-kinetic collisions. However, our infrared-ultraviolet double resonance (IRUVDR) experiments have demonstrated that collisional V-V transfer between the v₆ (in-plane wag, 989-cm⁻¹) and v₄ (out-of-plane bend, 938-cm⁻¹) vibrational modes of D₂CO is remarkably rapid, occurring with approximately gas-kinetic efficiency. The general IRUVDR excitation scheme employed in this context is illustrated in Fig. 1. Earlier studies^1,2 of D₂CO/D₂CO collisions have now been extended to a variety of collision partners (He, Ar, CH₄ N₂, N₂O), providing some control of the relative rates of v₆→v₄ transfer and of rotational relaxation with respect to quantum numbers J and K_a. The extraordinary efficiency of collision-induced v₆→v₄ transfer in D₂CO is attributable to the rovibrational mixing effect of Coriolis coupling and the availability of a number of efficient quasi-elastic relaxation channels.

© 1988 Optical Society of America