Tomographic Analysis of Diode Laser Absorbance Spectra

Absorbances measured using line-of-sight techniques inherently report spectral attenuation integrated along the entire beam path1. At a given frequency, line-of-sight absorbance through a low pressure combusting system may have contributions from gases at several different densities and temperatures corresponding to the light beam passing through different regions in the low pressure containment chamber. The degree to which the line-of-sight path is nonhomogeneous is determined by diffusion and flow dynamics within the low pressure containment chamber. Usually, the region of interest is the flame region where the density of some combustion gases may be less than in cooler portions of the line-of-sight path.