Atmospheric trace gas analysis with cavity ring-down spectroscopy |
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| Authors: | Daniel Kleine Manfred Mürtz Jörg Lauterbach Hannes Dahnke Wolfgang Urban Peter Hering Karl Kleinermanns |
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| Affiliation: | 1. Institut für Lasermedizin, Universität Düsseldorf, 40225 Düsseldorf, Germany;2. Institut für Lasermedizin, Universität Düsseldorf, 40225 Düsseldorf, Germany Institut für Physikalische Chemie I, Universität Düsseldorf, 40225 Düsseldorf, Germany;3. Institut für Angewandte Physik, Universität Bonn, 53115 Bonn, Germany;4. Institut für Physikalische Chemie I, Universität Düsseldorf, 40225 Düsseldorf, Germany |
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| Abstract: | Cavity ring-down spectroscopy (CRDS) is a highly sensitive laser absorption method. It can be used for quantitative analysis of molecular species at the sub-ppb level. The absorption cell (cavity) is sealed by two high-reflective mirrors on each side, which results in an effective absorption path-length of some kilometers. Our experiments for atmospheric gas analysis have been carried out so far with an Excimer pumped dye laser in the UV-VIS and a CO overtone sideband laser in the wavelength region around 3 μm. Experiments with an all solid-state difference frequency laser system will follow. In the UV-VIS region, we measured trace gas molecules like SO2, NO2, and CH2O. In the mid-infrared, around 3 μm, we measured hydrocarbons like CH4, C2H6, and C2H4 with a detection limit of less than 1 ppb. The noise equivalent absorption coefficients in the MIR are in the order of 1.7·10−9 cm−1. Due to the high data acquisition rate and the high sensitivity, CRDS enables real-time detection of trace gases in ambient air. |
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