A photoacoustic spectrometer for ozone detection

A high-resolution external laser photoacoustic spectrometer has been developed. The spectrometer was used to analyze the absorption transitions of the ozone (O-16(3)) in coincidence with the CO2 laser emission (9-10 mum) and to evaluate, its limit of sensitivity. A CO2 laser and a photoacoustic resonant cell, totally built in project, formed the spectrometer. The CO2 laser operates in 80 CW transitions distributed in the regular bands with power of up to 15W, tuned by a diffraction grating. The cell has frequency resonance of longitudinal mode close to 1600 Hz. The cell is equipped with two small electret microphones and ZnSe windows in Brewster angle. The quality factor of the cell was measured about 30 through the ozone absorption in resonance with the 9P14 line of CO2 laser. The spectrometer sensitivity limit was preliminary evaluated for ozone detection around 100ppb (214 mu gO(3)/m(3)).