A compact broadband cavity enhanced absorption spectrometer for detection of atmospheric NO2 using light emitting diodes

Abstract

A compact and low power detector has been developed for the in situ measurement of atmospheric NO₂ using broadband cavity enhanced absorption spectroscopy. Absorption by the O₂–O₂ collisional pair was used to determine the cavity mirror reflectivity, thus enabling the retrieval of absolute absorber concentrations by differential spectral fitting techniques. Quantitative amounts of ambient NO₂ (between 3 and 32 parts per billion) were retrieved from spectra recorded in the presence of ambient aerosol with statistical uncertainties approaching 100 ppt for a 60 s averaging period. The instrument's response was compared to that of a commercial chemiluminescence detector and was found to agree to within 6%.