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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Accepted Version
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
Journal Title
Journal ISSN
Volume Title
Publisher
ACS Publications
Published Version
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
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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