Open-path cavity ring-down spectroscopy for trace gas measurements in ambient air

Optics Express
Laura E McHaleAzer P Yalin

Abstract

The present work used a near-infrared methane cavity ring-down spectroscopy (CRDS) sensor to examine performance and limitations of open-path CRDS for atmospheric measurements. A simple purge-enclosure was developed to maintain high mirror reflectivity and allowed >100 hours of operation with mirror reflectivity above 0.99996. We characterized effects of aerosols on ring-down decay signals and found the dominant effect to be fluctuations by large super-micron particles. Simple software filtering approaches were developed to combat these fluctuations allowing noise-equivalent sensitivity of ~6x10(-10) cm(-1)HJ Hz(-1/2) within a factor of ~3 of closed-path systems (based on stability of the absorption baseline). Sensor measurements were validated against known methane concentrations in a closed-path configuration, while open-path validation was performed by side-by-side comparison with a commercial closed-path system.

References

Nov 25, 2003·Analytical Chemistry·John B DudekKevin K Lehmann
Mar 12, 2010·Applied Optics·Haifeng Huang, Kevin K Lehmann
Apr 2, 2010·Physical Chemistry Chemical Physics : PCCP·Rachael E H MilesJonathan P Reid
Sep 18, 2013·Proceedings of the National Academy of Sciences of the United States of America·David T AllenJohn H Seinfeld
Jan 22, 2015·Environmental Science & Technology·Ashley M PierceDaniel Obrist
Mar 10, 2015·Environmental Science & Technology·Tara I YacovitchCharles E Kolb
Jul 8, 2015·Environmental Science & Technology·Xin LanAzucena Torres

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