Incoherent broad-band cavity-enhanced absorption spectroscopy for simultaneous trace measurements of NO2 and NO3 with a LED source

• Published in: Applied physics. B, Lasers and optics Lasers and optics, 2010-11, Vol.101 (3), p.661-669
• Main Authors: Ventrillard-Courtillot, I., Sciamma O’Brien, E., Kassi, S., Méjean, G., Romanini, D.
• Format: Article
• Language: English
• Subjects: Air pollution; Air quality; Atomic Physics; Diagnostic software; Drift; Engineering; Instrumentation and Detectors; Lasers; Light-emitting diodes; Nitrogen dioxide; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Quantum Optics; Spectrometers; Urban environments
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-010-4253-x

In the past decade, due to a growing awareness of the importance of air quality and air pollution control, many diagnostic tools and techniques have been developed to detect and quantify the concentration of pollutants such as NO x , SO x , CO, and CO 2 . We present here an Incoherent Broad-Band Cavity-Enhanced Spectroscopy (IBB-CEAS) set-up which uses a LED emitting around 625 nm for the simultaneous detection of NO 2 and NO 3 . The LED light transmitted through a high-finesse optical cavity filled with a gas sample is detected by a low resolution spectrometer. After calibration of the spectrometer with a NO 2 reference sample, a linear multicomponent fit analysis of the absorption spectra allows for simultaneous measurements of NO 2 and NO 3 concentrations in a flow of ambient air. The optimal averaging time is found to be on the order of 400 s and appears to be limited by the drift of the spectrometer. At this averaging time the smallest detectable absorption is 2×10 −10  cm −1 , which corresponds to detection limits of 600 pptv for NO 2 and 2 pptv for NO 3 . This compact and low cost instrument is a promising diagnostic tool for air quality control in urban environments.