INFRARED-ULTRAVIOLET DOUBLE RESONANCE SPECTROSCOPY OF ACETYLENE: ROVIBRATIONAL ENERGY TRANSFER AT $11 600 CM^{-1}$

Abstract

Fluorescence-detected infrared-ultraviolet double resonance (IR-UV DR) experiments are used to monitor collisioninduced energy transfer processes which occur in the $""\nu_{2} + 3\nu_{3""$ region of the rovibrational manifold of gas-phase $C_{2}H_{2}$ at $11 600 cm^{-1}$, A Raman-shifted dye laser is used to prepare molecules in this region, followed by LIF probing in the $\tilde{A}-\tilde{X}$ vibronic band system. Collisional efficiency of rotationally-resolved V-V energy transfer between coupled rovibrational levels of the $\nu_{2} + 3\nu_{3}$ manifold is enhanced by the intramolecular perturbations (anharmonic, Coriolis, l-type). Rotationally-resolved kinetics of such processes and accompanying rotational energy transfer (RET) have been measured. RET is found to occur at a similar rate to that found for other vibrational manifolds in $C_{2}H_{2}$ and V-V energy transfer is found to be particuarly efficient. A master equation formalism is used to model the energy transfer quantitatively.