Photoacoustic Air Pollution Monitoring with an Isotopic CO₂ Laser

This paper considers the possibilities of using lasers based on rare isotopic species of carbon dioxide to detect trace quantities of pollutants in ambient air by photoacoustic spectroscopy (PA). The use of isotopic CO 2 ‐laser lines allows to overcome the background absorption of atmospheric carbon dioxide. The effect of water vapor continuum absorption is eliminated by decreasing the gas pressure in the PA cell. The spectroscopic analysis performed within the framework of GEISA‐84. Database shows that even at a 10%‐measurement error detection sensitivities of 0.1–10 ppbV for NH 3 , C 2 H 4 , O 3 , HNO 3 , PH 3 and ClO in ambient air can be achieved. A simple PA gas analyzer on the basis of a 13 C 16 O 2 ‐laser with a NH 3 sensitivity of ≠1 ppbV and a time resolution of 1.5 min is also described.