Effect of gas pressure and pulse length on the isotopically selective multiphoton dissociation of CF3Cl under CO2 laser pulses

Abstract

The multiphoton dissociation of CF3Cl induced by TEA-CO2 laser pulses has been studied in a focused beam geometry. TheR(10) [00°1–02°0] (\(\bar v = 1071.9cm^{ - 1} \)) laser line was used, so as to dissociate preferentially the minor isotopic component13CF3Cl. The isotopic selectivityS and the dissociation probability per pulse ω were measured in the pressure range between 0.25 and 8 Torr. With short laser pulses (90 ns FWHM),S is found to increase slightly with gas pressure up to 2 Torr, and ω, to increase almost linearly over the whole pressure range studied. A schematic model is proposed which satisfactorily explains these results if the transition rates across the energy level spectrum of the CF3Cl molecules are assumed to increase with gas pressure.