LASER-INDUCED PLASMAS IN AMBIENT AIR FOR INCOHERENT BROADBAND CAVITY-ENHANCED ABSORPTION SPECTROSCOPY

2015 ◽  
Author(s):  
Albert Ruth ◽  
Johannes Orphal ◽  
Sophie Dixneuf
Keyword(s):  
Absorption Spectroscopy ◽  
Ambient Air ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy

2020 ◽  
Author(s):  
Jingwei Liu ◽  
Xin Li ◽  
Yiming Yang ◽  
Haichao Wang ◽  
Cailing Kuang ◽  
...  
Keyword(s):  
Light Intensity ◽  
Light Source ◽  
Absorption Spectroscopy ◽  
Fiber Bundle ◽  
Ambient Air ◽  
Optical Path ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Near Ultraviolet ◽  
Type Fiber

<p>Formaldehyde (HCHO) is the most abundant atmospheric carbonyl compound and plays an important role in the troposphere. However, HCHO detection via traditional incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) is limited by short optical path lengths and weak light intensity. Thus, a new light-emitting diode (LED)-based IBBCEAS was developed herein to measure HCHO in ambient air. Two LEDs (325 and 340 nm) coupled by a Y-type fiber bundle were used as an IBBCEAS light source, which provided both high light intensity and a wide spectral fitting range. The reflectivity of the two cavity mirrors used herein was 0.99965 (1 – reflectivity = 350 ppm loss) at 350 nm, which corresponded with an effective optical path length of 2.15 km within a 0.84 m cavity. At an integration time of 30 s, the measurement precision (1σ) for HCHO was 380 parts per trillion volume (pptv) and the corresponding uncertainty was 8.3%. The instrument was successfully deployed for the first time in a field campaign and delivered results that correlated well with those of a commercial wet-chemical instrument based on Hantzsch fluorimetry (R<sup>2</sup> = 0.769). The combined light source based on Y-type fiber bundle overcomes the difficulty of measuring ambient HCHO via IBBCEAS in near-ultraviolet range, which may extend IBBCEAS technology to measure other atmospheric trace gases with high precision.</p>

Development of an incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for autonomous field measurements of HONO and NO2 in a rural area

2021 ◽  
Author(s):  
Lingshuo Meng ◽  
Gaoxuan Wang ◽  
Cécile Coeur ◽  
Alexandre Tomas ◽  
Tao Wu ◽  
...  
Keyword(s):  
Rural Area ◽  
Absorption Spectroscopy ◽  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Trace Gases ◽  
Ambient Air ◽  
Rural Site ◽  
Oh Radicals ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

<p>Nitrous acid (HONO) is one of the important atmospheric trace gases due to its contribution to the cycles of nitrogen oxides (NOx) and hydrogen oxides (HOx). In particular it acts as a precursor of tropospheric OH radicals, which is responsible for the self-cleansing capacity of the atmosphere [1,2]. We developed an instrument based on incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) for automatic measurement of HONO in a rural area in a summer period during a field "Campagne d’OBservation Intensive des Aérosols et précurseurs à Caillouël-Crépigny (COBIACC)" in France. IBBCEAS technique is now extensively used in field applications for the measurements of both trace gases and aerosols [3,4].</p><p>Real-time in situ measurements of HONO and NO<sub>2</sub> have been simultaneously carried out. The IBBCEAS instrument performance has been demonstrated and validated through lab-based tests, and in particular through field intercomparison via side-by-side measurements of temporal concentration profiles of HONO and NO<sub>2</sub> in the rural area. The intercomparison of the concentration measurements between IBBCEAS and an instrument called MARGA (Monitor for AeRosols and Gases in Ambient air) for HONO, and IBBCEAS vs. a reference NOx analyzer for NO<sub>2</sub>. Good agreements have been observed which demonstrated the performance of the developed IBBCEAS instrument for the measurement of atmospheric HONO concentration (<5 ppb) in a rural area.</p><p>The preliminary experimental results will be presented and discussed.</p><p><strong>Acknowledgments</strong> This work was supported by the CPER CLIMIBIO program and the Labex CaPPA project (ANR-10-LABX005). The authors highly appreciate the offers of Mr. Eric Wetzels from Polyfluor Plastics bv for the help in our instrumental conception involving Teflon pipe.</p><p><strong>References</strong></p><p>[1] X. Li, T. Brauers, R. Häseler, R. Bohn, H. Fuchs, A. Hofzumahaus, F. Holland, S. Lou, et al., Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China, Atmos. Chem. Phys. <strong>12</strong> (2012) 1497-1513.</p><p>[2] H. Su, Y. Cheng, M. Shao, D. Gao, Z. Yu, L. Zeng, J. Slanina, et al., Nitrous acid (HONO) and its daytime sources at a rural site during the 2004 PRIDE‐PRD experiment in China, J. Geophys. Res. <strong>113</strong> (2008) D14312.</p><p>[3] T. Wu, Q. Zha, W. Chen, Z. Xu, T. Wang, X. He, Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO<sub>2</sub> in Hong Kong, Atmos. Environ. <strong>95</strong> (2014) 544-551.</p><p>[4] L. Meng, G. Wang, P. Augustin, M. Fourmentin, Q. Gou, E. Fertein, T. N. Ba, C. Coeur, A. Tomas, W. Chen, Incoherent broadband cavity enhanced absorption spectroscopy-based strategy for direct measurement of aerosol extinction in lidar blind zone, Opt. Lett. <strong>45 </strong>(2020) 1611-1614.</p>

scholarly journals Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

2016 ◽  
Vol 9 (1) ◽  
pp. 41-52 ◽  
Author(s):  
R. A. Washenfelder ◽  
A. R. Attwood ◽  
J. M. Flores ◽  
K. J. Zarzana ◽  
Y. Rudich ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Absorption Spectroscopy ◽  
Spectral Region ◽  
Trace Gases ◽  
Ambient Air ◽  
Array Detector ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Ultraviolet Spectral Region ◽  
Standard Additions

Abstract. Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1− reflectivity  =  700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315–350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit  = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315–350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to trace gases, this approach will be appropriate for measurements of aerosol extinction in ambient air, and this spectral region is important for characterizing the strong ultraviolet absorption by brown carbon aerosol.

scholarly journals Quantification of nitrous acid (HONO) and nitrogen dioxide (NO<sub>2</sub>) in ambient air by broadband cavity-enhanced absorption spectroscopy (IBBCEAS) between 361–388 nm

2019 ◽  
Author(s):  
Nick Jordan ◽  
Hans D. Osthoff
Keyword(s):  
Absorption Spectroscopy ◽  
Optical Cavity ◽  
Ambient Air ◽  
Acquisition Time ◽  
Optical Extinction ◽  
Mixing Ratios ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Near Ultraviolet ◽  
Mirror Reflectivity

Abstract. This work describes a state-of-the-art, incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for quantification of HONO and NO2 mixing ratios in ambient air. The instrument is operated in the near-ultraviolet spectral region between 361 and 388 nm. The mirror reflectivity and optical cavity transmission function were determined from the optical extinction observed when sampling air and helium. To verify the accuracy of this approach, Rayleigh scattering cross-sections of nitrogen and argon were measured and found in quantitative agreement with literature values. The mirror reflectivity exceeded 99.98 %, at its maximum near 373 nm, resulting in an absorption pathlength of 6 km from a 1 m long optical cavity. The instrument precision was assessed through Allan variance analyses and showed minimum deviations of &amp;pm;58 pptv and &amp;pm;210 pptv (1σ) for HONO and NO2, respectively, at an optimum acquisition time of 5 min. Measurements of HONO and NO2 mixing ratios in laboratory-generated mixtures by IBBCEAS were compared to thermal dissociation cavity ring-down spectroscopy (TD-CRDS) data and agreed within combined experimental uncertainties. Sample ambient air data collected in Calgary are presented.

scholarly journals Quantification of nitrous acid (HONO) and nitrogen dioxide (NO<sub>2</sub>) in ambient air by broadband cavity-enhanced absorption spectroscopy (IBBCEAS) between 361 and 388 nm

2020 ◽  
Vol 13 (1) ◽  
pp. 273-285 ◽  
Author(s):  
Nick Jordan ◽  
Hans D. Osthoff
Keyword(s):  
Absorption Spectroscopy ◽  
Optical Cavity ◽  
Ambient Air ◽  
Acquisition Time ◽  
Optical Extinction ◽  
Mixing Ratios ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Near Ultraviolet ◽  
Mirror Reflectivity

Abstract. This work describes an incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for quantification of HONO and NO2 mixing ratios in ambient air. The instrument is operated in the near-ultraviolet spectral region between 361 and 388 nm. The mirror reflectivity and optical cavity transmission function were determined from the optical extinction observed when sampling air and helium. To verify the accuracy of this approach, Rayleigh scattering cross sections of nitrogen and argon were measured and found to be in quantitative agreement with literature values. The mirror reflectivity exceeded 99.98 %, at its maximum near 373 nm, resulting in an absorption path length of 6 km from a 1 m long optical cavity. The instrument precision was assessed through Allan variance analyses and showed minimum deviations of ±58 and ±210 pptv (1σ) for HONO and NO2, respectively, at an optimum acquisition time of 5 min. Measurements of HONO and NO2 mixing ratios in laboratory-generated mixtures by IBBCEAS were compared to thermal dissociation cavity ring-down spectroscopy (TD-CRDS) data and agreed within combined experimental uncertainties. Sample ambient air data collected in Calgary are presented.

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