Ammonia, the third most important abundant nitrogen compound, is a primary alkaline gas in the atmosphere. It has
strong absorption bands in the deep ultraviolet (DUV) spectral range and so can be reliably detected by the differential
optical absorption spectroscopy (DOAS) technique. A portable UV-DOAS gas sensor based on multi-pass cell has been
designed to detected trace gases, especially for ammonia, in the DUV spectral range, with good performance using a
broad-band Deuterium source and high-sensitivity spectrometer. With the optical path as long as 20m, such a sensor
could detected NH3 concentrations as low as 100ppb according to the result of in-situ measurement. Fast response time
and low measurement error of this portable gas sensor could be competent for emergency monitoring.
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