Laser‐Induced Saturated Fluorescence as a Method for the Determination of Radical Concentrations in Flames

The laser‐induced saturated fluorescence method was further developed with the aim of increasing the accuracy of radical concentration measurements in flames. Absolute number densities for CH and OH in a low‐pressure acetylene/oxygen flame were obtained from saturation curves based on a two‐level rate equation model, whose validity was checked for the experimental conditions. From these saturation curves, approximate oscillator strengths could be deduced, which could serve as a cross‐check for the evaluated number densities. Temperatures were determined from rotational spectra of the excited molecules. – For CH as well as for OH, the concentrations obtained with different excitation methods agree well with each other. They were compared with kinetic model calculations. For the extension of the saturated fluorescence method to higher pressures, a multi‐level model is being developed.