High-sensitivity measurement of OH radicals using multi-pass enhanced Faraday Rotation Spectroscopy
- 1Laboratoire de Physicochimie de l'Atmosphère / Université du Littoral Côte d'Opale - 59140 Dunkerque, France
- 2Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 230031 Hefei, China
The hydroxyl radical (OH) is considered as a primary agent responsible to remove a majority of trace gas in the atmosphere [1]. It is also responsible to initiate the reactions leading to the formation of a wide range of secondary species such as ozone (O3) and secondary organic aerosols (SOAs) [2]. Reliable and real-time assessment of the OH radical concentration change and related chemical process in the atmosphere is a key factor to understand and determinate the oxidation capacity of the atmosphere. Because of its very high reactivity, very short lifetime (≤ 1 s) associated with very low atmospheric concentration (~106 OH/cm3), the development of optical instrument allowing accurate, interference-free and ultra-high sensitivity in-situ direct measurement of OH concentration presents a great challenge for atmospheric science and climate change research.We report in this paper our recent development of an OH sensor based on Faraday Rotation Spectroscopy (FRS) [3]. FRS exploits magnetic circular birefringence (MCB) observed in the vicinity of Zeeman split absorption line of paramagnetic species such as O2, NO, NO2, OH. The Q(1,5e) and Q(1,5f) double lines of OH at 3568,52 cm-1 and 3568,41 cm-1 were chosen for quantification of OH radicals [4,5]. In order to enhance the detection sensitivity, multi-pass absorption approach was coupled to FRS. A 1σ (SNR=1) detection limit of about 5×107 OH/cm3 was achieved.
The experimental detail and the preliminary results will be presented and discussed.
Acknowledgments
The authors thank the financial supports from the CPER CLIMIBIO program and the Labex CaPPA project (ANR-10-LABX005).
References
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[2] D. Stone, L.K. Whalley, and D.E. Heard, Chem. Soc. Rev. 41 (2012) 6348-6404.
[3] G. Litfin, C.R. Pollock, R.F. Curl, F.K. Tittel, J. Chem. Phys. 72 (1980) 6602-6605.
[4] W. Zhao, G. Wysocki, W. Chen, et al., Opt. Express 19, (2011) 2493-2501.
[5] W. Zhao, G. Wysocki, W. Chen, W. Zhang, Appl. Phys. B 109 (2012) 511-519.
How to cite: Nguyen Ba, T., Zhao, W., Chen, J., Liu, K., Gao, X., Fertein, E., and Chen, W.: High-sensitivity measurement of OH radicals using multi-pass enhanced Faraday Rotation Spectroscopy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22371, https://doi.org/10.5194/egusphere-egu2020-22371, 2020
