Abstract: The principle object of the invention is to provide an improved particle analyzer for analyzing particles contained in a gaseous medium. A more specific object is to provide a particle analyzer that provides a measure of the concentration of particles of various sizes in the atmosphere and the make up of the particles of various sizes. A more specific object is to provide an analyzer of the foregoing type which is small inexpensive and suitable for unattended use in the field.

Abstract: A cross-road motor vehicle exhaust gas analyzer uses tunable infrared laser differential absorption spectroscopy incorporating photon infrared detection to determine the absolute fractional absorption of a laser by the gaseous medium. Spectroscopic constants of the gaseous species of interest are applied to the absolute fractional absorption to calculate the pertinent absolute column densities. In addition to a laser that sweeps across one or more absorption line of an component of interest, the system of the invention includes a laser source tunable over an absorption line of a reference species; the calculated column density of the reference species is used to normalize the concentration of the component of interest to the fuel consumption rate of the motor vehicle.