Hefei Research Institute has made progress in atmospheric nitrogen dioxide detection technology

NO2 is an important pollutant in the tropospheric atmosphere and plays an important role in the process of atmospheric composite pollution. Its highly sensitive and accurate measurement is of great significance to the research of atmospheric chemistry and the prevention and control of air pollution. The researchers developed a multimode laser-based amplitude-modulated cavity-enhanced absorption spectroscopy (AM-CEAS) technique, using a broadband multimode diode laser (center wavelength 406 nm) to achieve ultra-high sensitivity detection of NO2, sampling at 1s and 30s Under the same conditions, the detection limits reached 35 pptv and 8 pptv, respectively, which were four times lower than the detection limit of cavity ring-down absorption spectroscopy (CRDS) under the same conditions. The method uses ring-down time measurement, which can eliminate the process of cavity mirror reflectivity calibration and other processes, realize direct measurement of absolute concentration, and has the high optical injection efficiency of the coaxial cavity ring-down absorption spectrum and the low cavity of the off-axis cavity enhanced absorption spectrum. It has the advantages of film noise and narrow-band high-sensitivity weak signal detection of modulation spectrum. The instrument is simple, reliable, low-cost, self-calibrating, can run stably for a long time, and is free of manual maintenance, and has good scientific research and business application prospects.

Schematic diagram of the structure of Amplitude Modulated Cavity Enhanced Absorption Spectroscopy Technology Based on Broadband Multimode Laser

Comparison results of performance evaluation of amplitude modulation cavity-enhanced absorption spectroscopy and cavity ring-down absorption spectroscopy at different modulation frequencies