Long optical cavities for open-path monitoring of atmospheric trace gases and aerosol extinction

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Varma, Ravi M.
Venables, Dean S.
Ruth, Albert A.
Heitmann, Uwe M.
Schlosser, E.
Dixneuf, Sophie
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Optical Society of America
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An incoherent broadband cavity-enhanced absorption spectroscopy setup employing a 20 m long optical cavity is described for sensitive in situ measurements of light extinction between 630 and 690 nm. The setup was installed at the SAPHIR atmospheric simulation chamber during an intercomparison of instruments for nitrate (NO3) radical detection. The long cavity was stable for the entire duration of the two week campaign. A detection limit of similar to 2 pptv for NO3 in an acquisition time of 5 s was established during that time. In addition to monitoring NO3, nitrogen dioxide (NO2) concentrations were simultaneously retrieved and compared against concurrent measurements by a chemiluminescence detector. Some results from the campaign are presented to demonstrate the performance of the instrument in an atmosphere containing water vapor and inorganic aerosol. The spectral analysis of NO3 and NO2, the concentration dependence of the water absorption cross sections, and the retrieval of aerosol extinction are discussed. The first deployment of the setup in the field is also briefly described.
Atmospheric and oceanic optics , Air pollution monitoring , Spectroscopy
Varma, R. M.,Venables, D. S.,Ruth, A. A.,Heitmann, U.,Schlosser, E.,Dixneuf, S.; (2009) 'Long optical cavities for open-path monitoring of atmospheric trace gases and aerosol extinction'. Applied Optics, 48 (4):B159-B171. http://dx.doi.org/10.1364/AO.48.00B159
© 2009 Optical Society of America. This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/AO.48.00B159. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.