Retrieval of the concentration of hydrocarbons in air from opto-acoustic measurements

A retrieval technique for some hydrocarbon compounds (ethylene, ethanol, methanol, and isopropanol) concentration from opto-acoustic measurements of total absorption at several fixed wavelengths of the CO 2 -laser is presented in the report. In the gases concentration reconstructing, the method of least squares (LSM) as well as linear programming (LPM) and regularization (RM) methods were used. The problem of accuracy of the gases concentration retrieval depending on the quantity of simultaneously analyzed hydrocarbon compounds is discussed. Monitoring of gas composition of the atmospheric air by the optical absorption methods calls for instruments which are highly sensitive to absorption, highly selective, and capable of determining the concentration of trace gases in multicomponent mixtures. One of such instruments an opto-acoustic (OA) gas analyzer with a resonance cell. To analyze the content of gases under study, the atmospheric air, preliminary purified from atmospheric aerosol is pumped through the OA cell. Our work is aimed at studying of the accuracy of gas concentration reconstruction from OA measurements depending on: (1) error in determining the absorption coefficients K ij ; (2) available model of continuous absorption a c (v i ); (3) random error in measuring signals.