Real-time detection of 13CH4 in ambient air by use of mid-infrared cavity leak-out spectroscopy.
We report on spectroscopic real-time detection of (13)CH(4) in ambient air. Our measurements were carried out by means of cavity leak-out absorption spectroscopy employing a tunable cw laser in the mid-infrared spectral region near lambda = 3 microm. A CO laser in combination with tunable microwave sideband generation was used as the light source. Using a 50-cm-long ringdown cell with R = 99.98% mirrors, we achieved a detection limit of 290 parts in 10(12) (ppt) (13)CH(4) in ambient air (integration time, 100 s). The corresponding noise-equivalent absorption coefficient was 5 x 10(-9)/cm.
Kleine
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Institut für Lasermedizin, Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Dahnke
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Urban
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Hering
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Mürtz
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