Laser-induced fluorescence detection of atmospheric NO_(2) with a commercial diode laser and a supersonic expansion

摘要

Routine observations of atmospheric NO_(2) 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_(2) 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~(3) 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~(-1) (signal-to-noise ratio of 2), which is more than adequate for monitoring purposes.