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We developed a small size and light weight analyzer based on the broadband cavity enhanced absorption spectroscopy for measuring nitrogen dioxide (NO 2) with high spatial-temporal resolution and high accuracy. The instrument utilizes a LED centered at 450 nm, a short optical cavity, and a spectrometer to determine the extinction coefficients span 435–465 nm, allowing us to retrieve the mixing ratio of NO 2 by absorption cross-section. The measurement precision (1σ) for NO 2 is 98 ppt in 2 s under laboratory conditions. The uncertainty is estimated at 6% mainly attributed to cross-section and the mirror reflectivity. Good consistency was achieved by comparing with commercial chemiluminescence detector and cavity attenuation phase shift spectrometer (CAPS) (both R2 = 0.99). We further mounted the instrument on an unmanned aerial vehicle (UAV), and maintained the UAV flight at the height of 20 m, the comparative measurement with a CAPS set in a neighbor building with the same sampling height showed a good correlation (R2 = 0.97), which confirmed the instrumental feasibility and stability on the UAV platform. At last, we present a successful NO 2 vertical measurement test, the good performance indicates this portable technique has great potential for vertical measurement. In particular, the mini-CEAS technique can further extend to measure the vertical profiles of other trace gas species (such as nitrous acid) with strong optical structural absorptions, which would largely promote the understanding of atmospheric chemistry on a vertical scale. [Display omitted] • A mini and high-precision NO 2 analyzer based on cavity-enhanced absorption spectroscopy was developed. • Intercomparison with other techniques showed good consistency and confirmed its feasibility and robustness. • A successful NO 2 vertical measurement test was presented by the UAV system. [ABSTRACT FROM AUTHOR]

Dinitrogen pentoxide (N 2 O 5 ) is one of the basic trace gases which plays a key role in nighttime atmosphere. An intercomparison and validation of different N 2 O 5 measurement methods is important for determining the true accuracy of these methods. Cavity ring down spectroscopy (CRDS) and cavity enhanced absorption spectrometer (CEAS) were used to measure N 2 O 5 at the campus of the University of Chinese Academy of Sciences (UCAS) from February 21, 2016 to March 4, 2016. The detection limits were 1.6 ppt (1σ) at 30 s intervals for the CEAS instrument and 3.9 ppt (1σ) at 10 s time resolution for the CRDS instrument respectively. In this study, a comparison of the 1 min observations from the two instruments was presented. The two data sets showed a good agreement within their uncertainties, with an absolute shift of 15.6 ppt, slope of 0.94 and a correlation coefficient R 2 = 0.97. In general, the difference between the CRDS and CEAS instruments for N 2 O 5 measurement can be explained by their combined measurement uncertainties. However, high relative humidity (> 60%) and high PM2.5 concentration (> 200 μg/m 3 ) may contribute to the discrepancies. The excellent agreement between the measurement by the CRDS and CEAS instruments demonstrates the capability of the two instruments for accurately measuring N 2 O 5 with high sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: It has been proven that cavity enhanced absorption spectroscopy is a high sensitive spectral technique. The aim of our study was to apply this spectral technique to the detection of carbon monoxide with a narrow line width tunable DFB diode laser and high Q factor optical cavity. Absorption signals were extracted from a measurement recording the average of 20 highest light intensities that leak out of the cavity. The absorption spectrum of CO centered at 6354.18cm−1 was recorded; the experiment results indicate that cavity enhanced absorption spectroscopy could produce accurate high resolution spectrum. A detection sensitivity about 5.687×10−7 cm−1 has been achieved in a 45cm-long cell. [Copyright &y& Elsevier]

Abstract: The determination of gas-phase rate coefficients using the traditional discharge-flow system has produced a wealth of information that has informed atmospheric science. However, the range of pressure and temperatures observed in the Earth''s atmosphere cannot be accessed by such a system. In this paper we discuss the recent advances in flow tube studies such as the use of turbulent flow that have allowed one to operate flow systems at atmospheric pressure and over a wider range of temperature. At the same time a number of new detection methods have been coupled to flow systems, such as CIMS, CEAS and UV-PES that have greatly enhanced the versatility and range of systems that may be studied and these are briefly discussed. [Copyright &y& Elsevier]

• A nitrogen dioxide laser sensor was used to detect residue after an explosion. • The NO 2 concentration was determined for various explosives and distances. • Our method is fast, sensitive and robust against field conditions. We are presenting an application of optoelectronic nitrogen dioxide (NO 2) analyzer based on cavity enhanced absorption spectroscopy in the detection of traces of explosives after detonation. It has been shown that the analyzer using blue-violet laser is able to detect explosive residues after the detonation of various amounts of nitroaromatic compounds (75 g–1 kg) with higher efficiency than the HPLC soil sample testing equipment, which is the common standard in the analysis of explosives. Field studies have shown that it provided quick results, the amplitudes of which were about 8 dB despite the fact that NO 2 in the air was 3 orders of magnitude smaller than explosives found in soil. The NO 2 concentration after an explosion of different explosives at the distance of up to 20 m from the crater was 21-137 ppb, which was also dependent on the time between the explosion and the measurement, temperature and humidity of the atmospheric air and wind speed. [ABSTRACT FROM AUTHOR]