Time-resolved thermal lensing studies of laser-induced translational energy fluctuations in CD4, SO2, and OCS

Abstract

Translational energy changes caused by nonresonant vibration‐vibration (V‐V) and vibration → translation/rotation (V → T/R) processes have been studied in laser‐excited CD4, SO2, and OCS by the time‐resolved thermal lensing technique. Kinetic cooling has been observed in CD4 and SO2, indicating the contribution of endothermic collisional processes to the vibrational relaxation of these molecules. Varying amplitude of the cooling observed in CD4 has been attributed to rotational relaxation effects. A generalized spectrophone effect has been observed in mixtures of laser‐excited CH3F with CH3Cl. The sensitivity of the thermal lens to very weak absorption is discussed with regard to possible trace impurity detection. A discussion of the effects of acoustic phenomena is also presented.