DEPENDENCE OF FLUORESCENCE FROM LASER IRRADIATED SIF4 ON THE CO2-LASER WAVELENGTH

The energy per unit area necessary for the occurrence of visible fluorescence from dissociation products of laser irradiated SiF//4 has been measured for several values of CO//2 laser wavelength and gas pressure. Fluorescence was observed at a lower irradiance when the laser was tuned far from the nu //3 absorption band of SiF//4 than when the laser was coincident with the absorption band. In the latter case the irradiance required for dissociation decreased as gas pressure was increased from 2 to 10 Torr. However, for nonresonant excitation the irradiance required increased with increasing pressure in the same pressure range. In addition the temporal response of the fluorescence to the exciting radiation was found to depend upon the laser wavelength.