Role of Spectral Line Profile in Laser IR Analysis of Multicomponent Gas Mixtures

Abstract

Topical issues of the quantitative analysis of multicomponent gas mixtures with use of laser absorption infrared technologies are addressed. It is shown that a number of questions exist regarding the detection of pollutants using these technologies, and these concern not only the position of the center of the analytical line of the detected substance but also the shape of its profile, especially in case of strong intermolecular interactions under conditions of open atmosphere. A number of examples show various aspects of the influence of the error of the spectroscopic model embedded in the solution of the inverse problem (the width and shape of the laser spectral line and gas absorption lines) on the determination of gas concentrations. The parameters of the sensitivity and selectivity of laser gas analysis that support making the optimal choice of laser radiation frequencies for studying specific gas mixtures are discussed. The importance of the high monochromaticity of laser lines, the smooth tuning of the radiation frequency over a wide spectral range, and the adequate simulation of the IR spectra of multicomponent gas mixtures are demonstrated.