# A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications

We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of inline-formulaNOx, IO, CHOCHO and inline-formulaO3 in the 400–475 nm wavelength region. The instrument relies on the injection of a high-power LED source in a high-finesse cavity (inline-formulaF∼33 100), with the transmission signal being detected by a compact spectrometer based on a high-order diffraction grating and a charge-coupled device (CCD) camera. A minimum detectable absorption of inline-formula $M5inlinescrollmathmlnormal 2.0×{normal 10}^{-normal 10}$ 55pt14ptsvg-formulamathimgc253330af05f9acfa3f592b912e803f1 amt-13-4317-2020-ie00001.svg55pt14ptamt-13-4317-2020-ie00001.png  cminline-formula−1 was achieved within inline-formula∼22 min of total acquisition, corresponding to a figure of merit of inline-formula $M8inlinescrollmathmlnormal 1.8×{normal 10}^{-normal 10}$ 55pt14ptsvg-formulamathimgb39a0ddd7bc1f580cf5511ce992fd803 amt-13-4317-2020-ie00002.svg55pt14ptamt-13-4317-2020-ie00002.png  cminline-formula−1 Hzinline-formula $M10inlinescrollmathml{}^{-normal 1/normal 2}$ 21pt11ptsvg-formulamathimgb5319093eda405571bf1c434867fb212 amt-13-4317-2020-ie00003.svg21pt11ptamt-13-4317-2020-ie00003.png per spectral element. Due to the multiplexing broadband feature of the setup, multi-species detection can be performed with simultaneous detection of inline-formulaNO2, IO, CHOCHO and inline-formulaO3 achieving detection limits of 11, 0.3, 10 ppt (parts per trillion) and 47 ppb (parts per billion) (1inline-formulaσ) within 22 min of measurement, respectively (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). The implementation on the inlet gas line of a compact ozone generator based on electrolysis of water allows for the measurement of inline-formulaNOx (inline-formulaNO+NO2) and therefore an indirect detection of NO with detection limits for inline-formulaNOx and NO of 10 and 21 ppt (1inline-formulaσ), respectively. The device has been designed to fit in a 19 in., 3U (5.25 in.) rack-mount case; weighs 15 kg; and has a total electrical power consumption of inline-formula<300 W. The instrument can be employed to address different scientific objectives such as better constraining the oxidative capacity of the atmosphere, studying the chemistry of highly reactive species in atmospheric chambers as well as in the field and looking at the sources of glyoxal in the marine boundary layer to study possible implications on the formation of secondary aerosol particles.

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Barbero, Albane / Blouzon, Camille / Savarino, Joël / et al: A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications. 2020. Copernicus Publications.

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