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Laboratory and in situ mid-infrared spectroscopy techniques for the detection of atmospheric trace gases

Measurements of the volume mixing ratio of atmospheric constituents strongly rely on mid-IR spectroscopic remote sounding acquisitions from satellite, balloon-borne or ground-based platforms. The processing of the raw experimental data is currently limited by our knowledge of the line positions, intensities, and optical constants of each individual molecule. Intensive studies of the spectroscopic signatures of trace gases are essential to take full advantage of atmospheric measurement data.

Traditionally, mid-infrared spectroscopy of trace gases had been performed using Fourier transform infrared spectroscopy. However room temperature mid-infrared tunable lasers based on difference-frequency generation or quantum cascade sources are gradually becoming available. This opens an exciting new range of opportunities for not only laboratory measurements but also in situ acquisitions.

This presentation will provide an overview of the principle, advantages, and drawbacks of laboratory Fourier transform spectroscopy and will introduce a number of mid-IR laser spectroscopy techniques under development.