Oxygen-atom concentrations measured in flames: a method to improve the accuracy of laser-induced fluorescence diagnostics

A procedure is proposed, denoted as the corrected laser-induced fluorescenc e (LIF) method, that reduces the error associated with the unavoidable phot odissociation of O-2 molecules that has limited the measurement of oxygen-a tom concentrations in the past. Two different laser intensities are employe d, and the two signals that are obtained with two-photon LIF diagnostics ar e used to correct for the photolysis error. We measured oxygen-atom concent rations using this method at 33 locations in lean and rich flames. Results are compared with values determined by use of two independent techniques: t he partial equilibrium method and equilibrium calculations. The measurement s also quantify the shot noise, the photolysis errors, and the critical las er intensity required to avoid photolysis errors. (C) 2001 Optical Society of America.