Abstract

A number of gas analysis systems based on lead chalcogenide diode laser spectroscopy have been developed recently in our laboratory for both ¡mission and emission measurement on gas samples in nearly Doppler-limited conditions. Here we describe two instruments. One was conceived for atmospheric trace gas monitoring using derivative signal processing and the other one for car exhaust gas analysis with millisecond time resolution using a pulsed integrative signal processing scheme. Both systems rely on specific diode laser properties as tunability, narrow linewidth, diffraction-limited beam quality, and high modulation rate. In atmospheric trace gas monitoring with unattended operation over several days, detection limits between 50 ppt and 1 ppb were obtained for NO₂, HNO₃, NO, and SO₂. In time-resolved analysis of NO and CO in car exhaust gas, a rise time below 10 ms was found. Such a value is sufficient to resolve the emission related to a single stroke of one cylinder of the engine and will allow for an efficient optimization of the dynamic engine parameters in view of low fuel consumption and pollution levels.

© 1989 Optical Society of America