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www.atmos-meas-tech-discuss.net/1/481/2008/
doi:10.5194/amtd-1-481-2008
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Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) – applicability and corrections
1Institute for Environmental Physics (IUP), Ruprecht-Karls-University, Heidelberg, Germany
2Institute for Meteorology and Climate Research, Aerosols and Heterogeneous Chemistry in the Atmosphere (IMK-AAF), Forschungszentrum Karlsruhe GmbH, Germany
Abstract. Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broad band light sources, the broad-band CEAS (BB-CEAS). BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light path by the trace gas absorption, since cavity losses due to absorption by gases reduce the quality (Q) of the cavity. In fact, at wavelength, where the quality of the BB-CEAS cavity is dominated by the trace gas absorption (esp. at very high mirror reflectivity), the light path will vary inversely with the trace gas concentration and the strength of the band will become nearly independent of the trace gas concentration c in the cavity, rendering the CEAS Method useless for trace gas measurements. Only in the limiting case where the mirror reflectivity determines Q at all wavelength, the strength of the band as seen by the BB-CEAS instrument becomes proportional to the concentration c. We investigate these relationships in detail and present methods to correct for the cases between the two above extremes, which are of course the important ones in practice.
Discussion Paper (PDF, 638 KB) Interactive Discussion (Closed, 3 Comments) Final Revised Paper (AMT)
Notice on Discussion StatusCitation: Platt, U., Meinen, J., Pöhler, D., and Leisner, T.: Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) – applicability and corrections, Atmos. Meas. Tech. Discuss., 1, 481-507, doi:10.5194/amtd-1-481-2008, 2008. Bibtex EndNote Reference Manager XML
