Technical Note: Using a high finesse optical resonator to provide a long light path for differential optical absorption spectroscopy: CE-DOAS J. Meinen1,2, J. Thieser2,*, U. Platt2, and T. Leisner1,2 1Institute for Meteorology and Climate Research, Aerosols and Heterogeneous Chemistry in the Atmosphere (IMK-AAF), Karlsruhe Institute of Technology (KIT), Germany 2Institut for Environmental Physics (IUP), Atmosphere and Remote Sensing, Ruprecht-Karls-Universität Heidelberg, Germany *now at: Department of Atmospheric Chemistry, Max Planck Institute for Chemistry, Mainz Germany
Abstract. Cavity enhanced methods in absorption spectroscopy have seen a considerable
increase in popularity during the past decade. Especially Cavity Enhanced
Absorption Spectroscopy (CEAS) established itself in atmospheric trace gas
detection by providing tens of kilometers of effective light path length
using a cavity as short as 1 m. In this paper we report on the construction
and testing of a compact and power efficient light emitting diode based
broadband Cavity Enhanced Differential Optical Absorption Spectrometer
(CE-DOAS) for in situ observation of atmospheric NO3. This device
combines the small size of the cavity with the advantages of the DOAS
approach in terms of sensitivity, specificity and insensivity to intensity
fluctuations of the light source. In particular, no selective removal of the
analyte (here NO3) is necessary for calibration of the instrument if
appropriate corrections are applied to the CEAS theory. Therefore the
CE-DOAS technique can – in principle – measure any gas detectable by DOAS.
We will discuss the advantages of using a light emitting diode (LED) as
light source particularly the precautions which have to be considered for
the use of LEDs with a broad wavelength range. The instrument was tested in
the lab by detecting NO3 formed by mixing of NO2 and O3 in
air. It was then compared to other trace gas detection techniques in an
intercomparison campaign in the atmosphere simulation chamber SAPHIR at
Forschungszentrum Jülich at NO3 concentrations as low as 6.3 ppt.
Citation: Meinen, J., Thieser, J., Platt, U., and Leisner, T.: Technical Note: Using a high finesse optical resonator to provide a long light path for differential optical absorption spectroscopy: CE-DOAS, Atmos. Chem. Phys., 10, 3901-3914, doi:10.5194/acp-10-3901-2010, 2010.