Infrared multiphoton energy deposition in CF2HCl

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Abstract
Energy absorption by CF2HCl from an intense CO2 laser pulse is measured as a function of the laser energy fluence, the temperature, the pressure of CF2HCl, and the pressure of Ar bath gas. For collision free multiphoton absorption the average number of photons absorbed per molecule increases from two to neary 12 when the fluence is increased from 1.6 to 10.9 J cm−2 at 298 K. Comparison of absorption and dissociation data measured under identical conditions indicates relatively wide internal energy distributions produced by the multiphoton excitation. At 3 J cm−2 the average number of photons absorbed per molecule increases with increasing temperature betwen 300 and 450 K, whereas in the same temperature range at 10.7 J cm−2 a pronounced maximum is found in the absorption near 370 K. In the presence of 1 atm of added argon, an average of as many as 100 photons per molecule of CF2HCl can be absorbed as compared to the 18 photons necessary for collisionless dissociation.