Accueil > Équipes scientifiques > Systèmes Moléculaires, Astrophysique et Environnement (SYSTEMAE) > Outils expérimentaux > Cavity Ring Down Spectroscopy (CRDS)
Cavity Ring Down Spectroscopy (CRDS)
This technique generally consists in measuring the decay time of a laser pulse fired into a rigid high finesse optical cavity made of two highly reflective spherical mirrors. When the cavity is empty, the decay time depends only on the speed of light, on the mirror reflectivity and on the cavity length. When an absorbing specie fills the cavity, the decay time decreases. By measuring the decay time constant for the empty and for the filled cavity, it is therefore possible to obtain the absorption cross-section of the species. By scanning the wavelength, this technique becomes a very sensitive tool for absorption spectroscopy and for quantitative studies of extremely weak absorption bands. We use this technique in combination with a cell or a free jet. Laser photolysis or RF plasma source may also be coupled to this technique to produce and study radical or ionic species.