Development of a compact 406 nm diode laser-based cavity-enhanced spectrometer for high-sensitive detection of NO₂ levels in exhaust gas

Abstract

Nitrogen dioxide (NO2) is an important air pollutant due to its environmental impact and adverse effects on human health. It is released into the atmosphere primarily through anthropogenic activities. Here, we report on the development of a simple, compact, and cost-effective robust optical detection method exploiting cavity-enhanced absorption spectroscopy for high-sensitive and selective measurement of NO2 levels in real-time using a visible diode laser operating at 406 nm. A typical detection limit of ∼330 ppb for NO2 was achieved with an optimum acquisition time of ∼3.9 s, at optimal cavity pressure of 100 Torr. The sensor system demonstrates an effective optical path-length of 180 m in a high-finesse 50 cm long optical cavity in an interference-free spectral region and aerosol-free conditions. The spectrometer was optimized, calibrated, and demonstrated for the detection of NO2 levels in vehicular exhaust gases.

Oxygen-Isotope Exchange between CO2 and NO2 with Implications for Atmospheric Chemistry

“…To investigate the exchange of oxygen isotopes between N 16 O 2 and 18 O 12 C 16 O, we recorded the concentrations of 16 O 12 C 16 O and 18 O 12 C 16 O by the ICOS technique. The concentration of NO 2 was measured by our recently developed cavity-enhanced absorption spectroscopy (CEAS) technique, which traces the UV–visible absorption spectra of NO 2 at 406 nm . As both isomers of NO 2 exhibit similar electronic energy levels, they result in analogous UV–visible absorption characteristic features.…”