Collisional Radiative Involvement of Molecules into Resonance with the IR Laser Field in a Two-Component Molecular Medium

Abstract

Collisional radiative involvement of molecules not absorbing IR laser radiation into resonance with a laser field has been investigated for the case when nonabsorbing and absorbing molecules are laser-irradiated in a two-component medium. Experiments have been conducted with a CF₂HCl/CF₃Br mixture at a 1/1 pressure ratio. Molecules have been excited by a pulsed CO₂ laser. Two types of experiments have been considered: (i) molecules were irradiated under nonequilibrium thermodynamic conditions due to a compression shock wave arising before the solid surface when it was subjected to a supersonic pulsed gasdynamically cooled molecular flux and (ii) molecules were irradiated under static conditions with a gas in the cell kept at room temperature. It has been found that when molecules vibrationally cooled in the compression shock wave (in this case, their IR absorption bands are narrow; the FWHM is 7–8 cm^–1) are irradiated, initially nonabsorbing CF₂HCl molecules get effectively involved into resonance with the laser field. Their effective dissociation (with dissociation yield β ≥ 10–15%) has been discovered when the CF₂HCl/CF₃Br mixture was irradiated under the condition of CO₂ laser frequency detuning by more than 15–25 cm^–1 from the center of the IR absorption band of molecules vibrationally cooled in the compression shock wave. If molecules are irradiated at room temperature (the gas temperature in the cell), in which case the IR absorption band of molecules is rather wide (25–30 cm^–1), the collisional radiative involvement of CF₂HCl molecules into interaction with the laser field, albeit less pronounced, persists.