Using a pulsed dye laser and a nonresonant optoacoustic detector, the absorption spectrum of NO2 has been measured in the spectral region of 480–625 nm at various cell pressures and at various concentrations in air. The results of the measurements as a function of NO2 concentration in air demonstrate the detection capability of the system. An extrapolated sensitivity of 4 ppb NO2/W of laser power has been achieved.
P. C. Claspy, Chang Ha, and Yoh-Han Pao, "Optoacoustic detection of NO2 using a pulsed dye laser," Appl. Opt. 16, 2972-2973 (1977)