Routine observations of atmospheric NO<sub>2</sub> at concentrations ranging from 0.1 to 100 parts per billion are needed for air quality monitoring and for the evaluation of photochemical models. We have designed, constructed, and field tested a relatively inexpensive and specific NO<sub>2</sub> sensor using laser-induced fluorescence. The instrument combines a commercial cw external-cavity tunable diode laser (640 nm) and a continuous supersonic expansion. The total package is completely automated, has a modest size of 0.5 m<sup>3</sup> and 118 kg, and could be manufactured at competitive prices with the current generation of instruments. The sensitivity of the instrument is 145 parts per trillion by volume min<sup>−1</sup> (signal-to-noise ratio of 2), which is more than adequate for monitoring purposes.
© 2002 Optical Society of America
(010.1120) Atmospheric and oceanic optics : Air pollution monitoring
(010.1280) Atmospheric and oceanic optics : Atmospheric composition
(300.2530) Spectroscopy : Fluorescence, laser-induced
(300.6260) Spectroscopy : Spectroscopy, diode lasers
Patricia A. Cleary, Paul J. Wooldridge, and Ronald C. Cohen, "Laser-induced fluorescence detection of atmospheric NO2 with a commercial diode laser and a supersonic expansion," Appl. Opt. 41, 6950-6956 (2002)