Amplitude-modulated cavity-enhanced absorption spectroscopy with phase-sensitive detection: A new approach applied to the fast and sensitive detection of NO2

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MS-NO2-R1-v20220130-Final.pdf(1.49 MB)
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Date
2022-02-10
Authors
Zhou, Jiacheng
Zhao, Weixiong
Zhang, Yang
Fang, Bo
Cheng, Feihu
Xu, Xuezhe
Ni, Shichuan
Zhang, Weijun
Ye, Chunxiang
Chen, Weidong
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ACS Publications
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Abstract
Accurate and sensitive measurements of NO2 play an extremely important role in atmospheric studies. Increasingly, studies require NO2 measurements with parts per trillion by volume (pptv-level) detection limits. Other desirable instrument attributes include ease of use, long-term stability, and low maintenance. In this work, we report the development of an amplitude-modulated multimode-diode-laser-based cavity-enhanced absorption spectroscopy (AM-CEAS) system operating at 406 nm that uses phase-sensitive detection for extremely sensitive NO2 detection. The laser was TTL-modulated at 35 kHz. The mirror reflectivity was determined to be 99.985% based on the ring-down time measurement. The cavity base length was 47.5 cm, giving an effective absorption pathlength of ∼3.26 km. AM-CEAS achieved a 1σ detection precision of 35 pptv in a 1 s data acquisition time (4.98 × 10–10 cm–1), over 4 times lower than that attained using a ring-down approach and the same optical system. The AM-CEAS precision improved to 8 pptv over a data acquisition time of 30 s (1.14 × 10–10 cm–1). The AM-CEAS method with the multimode diode laser integrates the advantages of high light injection efficiency like on-axis alignment cavity ring-down spectroscopy, low cavity-mode noise like off-axis alignment CEAS, and narrow-bandwidth high-sensitivity weak signal detection of modulation spectroscopy, providing a powerful, straightforward, and general method for ultrasensitive absorption and extinction measurements.
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Keywords
Amplitude-modulated multimode-diode-laser-based cavity-enhanced absorption spectroscopy system , AM-CEAS , NO2
Citation
Zhou, J., Zhao, W., Zhang, Y., Fang, B., Cheng, F., Xu, X., Ni, S.,Zhang, W., Ye, C., Chen, W. and Venables, D. S. (2021) 'Amplitude-modulated cavity-enhanced absorption spectroscopy with phase-sensitive detection: A new approach applied to the fast and sensitive detection of NO2', Analytical Chemistry, 94(7), pp. 3368-3375. doi: 10.1021/acs.analchem.1c05484
Copyright
© 2022, American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Analytical Chemistry, after technical editing by the publisher. To access the final edited and published work see: https://doi.org/10.1021/acs.analchem.1c05484