The most important factor determining the response of systems to high-intensity infrared radiation is the quantity of vibrational energy deposited in the absorbing molecules. Determination of this quantity is complicated by spatial nonuniformities in the infrared radiation fluence and by distributions over energy in the system. In this paper, we obtain expressions for the infrared fluence distribution in a focused Gaussian beam. This is combined with an empirical model for the excitation function (0) to calculate energy deposition for a range of parameters. These results are compared with available experimental data on dissociation yields for sulfur hexafluoride, and also to various approximate results. Finally, we consider the advantages and limitations of several possible experimental approaches to determining the absolute excitation level of molecules and microscopic energy distributions in the focal volume of the laser beam.
Jeffrey I Steinfeld,
"Energy Deposition In Molecules Resulting From Multiple Infrared Photon Absorption," Optical Engineering 19(1), 190102 (1 February 1980). https://doi.org/10.1117/12.7972463