High-accuracy and high-sensitivity spectroscopic measurement of dinitrogen pentoxide (N2O5) in an atmospheric simulation chamber using a quantum cascade laser. Issue 24 (15th September 2017)

• Record Type: Journal Article
• Authors: Yi, Hongming; Wu, Tao; Lauraguais, Amélie; Semenov, Vladimir; Coeur, Cecile; Cassez, Andy; Fertein, Eric; Gao, Xiaoming; Chen, Weidong
• Is Part Of: Analyst. Volume 142:Issue 24(2017)
• Page Start: 4638
• Page End: 4646
• Publication Date: 2017-09-15
• Subjects: Chemistry, Analytic -- Periodicals; 543
• DOI: 10.1039/c7an01167a
• Languages: English
• ISSNs: 0003-2654

Abstract

Abstract : A spectroscopic instrument based on a mid-infrared external cavity quantum cascade laser was developed for high-accuracy measurements of N2 O5 at the ppbv-level. Abstract : A spectroscopic instrument based on a mid-infrared external cavity quantum cascade laser (EC-QCL) was developed for high-accuracy measurements of dinitrogen pentoxide (N2 O5 ) at the ppbv-level. A specific concentration retrieval algorithm was developed to remove, from the broadband absorption spectrum of N2 O5, both etalon fringes resulting from the EC-QCL intrinsic structure and spectral interference lines of H2 O vapour absorption, which led to a significant improvement in measurement accuracy and detection sensitivity (by a factor of 10), compared to using a traditional algorithm for gas concentration retrieval. The developed EC-QCL-based N2 O5 sensing platform was evaluated by real-time tracking N2 O5 concentration in its most important nocturnal tropospheric chemical reaction of NO3 + NO2 ↔ N2 O5 in an atmospheric simulation chamber. Based on an optical absorption path-length of L eff = 70 m, a minimum detection limit of 15 ppbv was achieved with a 25 s integration time and it was down to 3 ppbv in 400 s. The equilibrium rate constant K eq involved in the above chemical reaction was determined with direct concentration measurements using the developed EC-QCL sensing platform, which was in good agreement with the theoretical value deduced from a referenced empirical formula under well controlled experimental conditions. The present work demonstrates the potential and the unique advantage of the use of a modern external cavity quantum cascade laser for applications in direct quantitative measurement of broadband absorption of key molecular species involved in chemical kinetic and climate-change related tropospheric chemistry.