On the Measurement of the Rate of Intramolecular Vibrational EnergyRedistribution via High Resolution Molecular Beam OptothermalSpectroscopy

Using frequency resolved techniques we have been able to measure the rate of intramolecular vibrational energy redistribution in a number of substituted acetylenes. The method of IVR rate determination is discussed with respect to time domain measurements. The lifetimes we have determined have been quite long, ranging from a few hundred ps to a few ns. Interesting behavior of the rate as a function of the structure of the molecule has been observed. Results show sensitivity of the IVR rate to heavy mass substitution and the possibility of chromophore determined lifetimes.