LASER-INDUCED SATURATED FLOURESCENCE INVESTIGATIONS OF CH, CN AND NO RADICALS IN LABORATORY FLAMES

Author Institution:Laser-induced saturated fluorescence appears attractive for the remote, spatially-precise, in situ measurement of flame radical concentration at trace levels. Fluorescence from CH, CN and NO radicals was observed in appropriate laboratory flames operating at atmosphere pressure. Excitation of the fluorescence was generated by tunable, narrowband dye lasers, pumped by suitable harmonics of a 10 Hz, 10 nanosecond pulsed neodymium: YAG laser. Because of the high dye laser spectral intensities, saturation of CH and CN fluorescence was easily attained. Concentrations of these two species were estimated through use of a simplified model which accounts for rotational redistribution. The model will be briefly described. The fluorescence measurements were in good agreement with absorption measurements. Laser-induced NO fluorescence was observed, but saturation was not attained for incident laser intensities up to $6\times 10^{6}$ $W/cm^{2}-cm^{1}$