DISTURBANCE OF LASER-INDUCED-FLUORESCENCE MEASUREMENTS OF NO IN METHANE-AIR FLAMES CONTAINING CHLORINATED SPECIES BY PHOTOCHEMICAL EFFECTS INDUCED BY 225-NM-LASER EXCITATION

Laser-induced fluorescence measurements of NO in CH4 air flames seeded with CH3Cl and CH2Cl2 are described. The measurements are perturbed b y strong photochemical effects characterized by UV emissions. The cont ribution of these background emissions is taken into account on the ba sis of an on-line-off-line resonance procedure. First results indicate an important increase of NO in the presence of chlorinated species. B ackground emissions observed in the range 220-260 nm and at 278 nm are ascribed, respectively, to electronically excited HCl and CCl photofr agments. It is shown that C2H3Cl and CHCl2, species are responsible fo r the formation of HCl and CCl, respectively, and a photolytic mechani sm for formation of the photofragments is proposed. (C) 1998 Optical S ociety of America.