Chemically reactive short-lived species play a crucial role in tropospheric processes affecting regional air quality and global climate change. Contrary to long-lived species (such as greenhouse gases), fast, accurate and precise monitoring changes in concentration of atmospheric short-lived species represents a real challenge due to their short life time (~1 s for OH radical) and very low concentration in the atmosphere (down to 10⁶ molecules/cm3, corresponding to 0.1 pptv at standard temperature and pressure). We report on our recent progress in instrumentation developments for spectroscopic sensing of trace reactive species. Modern photonic sources such as quantum cascade laser (QCL), distributed feedback (DFB) diode laser, light emitting diode (LED), difference-frequency generation (DFG) parametric source are implemented in conjunction with highsensitivity spectroscopic measurement techniques for : (1) nitrous acid (HONO) monitoring by QCL-based long optical pathlength absorption spectroscopy and LED-based IBBCEAS (incoherent broadband cavity-enhanced absorption spectroscopy); (2) DFB laser-based hydroxyl free radical (OH) detection using WM-OA-ICOS (wavelength modulation off-axis integrated cavity output spectroscopy) and FRS (Faraday rotation spectroscopy), respectively; (3) nitrate radical (NO3) and nitrogen dioxide (NO2) simultaneous measurements with IBBCEAS approach. Applications in field observation and in smog chamber study will be presented.

Date Published: 4 February 2013
PDF: 11 pages
Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X, 86310Y (4 February 2013); doi: 10.1117/12.2004803

Published in SPIE Proceedings Vol. 8631:
Quantum Sensing and Nanophotonic Devices X
Manijeh Razeghi, Editor(s)