Using a high finesse optical resonator to provide a long light path for differential optical absorption spectroscopy: CE-DOAS

J. Meinen (1, 2) , J. Thieser (2) , U. Platt (2) , T. Leisner (1, 2)

1 IMK - Institute for Meteorology and Climate Research
2 IUP - Institute of Environmental Physics [Heidelberg]

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 field observation of atmospheric NO₃. This device combines the small size of the cavity with the enormous advantages of the DOAS approach in terms of sensitivity and specificity. In particular, no selective removal of the analyte (here NO₃) is necessary, thus 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 satisfied for the use of LEDs. The instrument was tested in the lab by detecting NO₃ in a mixture 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 NO₃ concentrations as low as 6.3 ppt.

Domaines: Océan, Atmosphère

J. Meinen, J. Thieser, U. Platt, T. Leisner. Using a high finesse optical resonator to provide a long light path for differential optical absorption spectroscopy: CE-DOAS. Atmospheric Chemistry and Physics Discussions, 2008, 8 (3), pp.10665-10695. ⟨hal-00304229⟩