Measurement of reactive atmospheric species by ultraviolet cavity-enhanced spectroscopy with a mode-locked femtosecond laser.
We demonstrate the possibility of measuring parts in 10(12) by volume concentrations of radicals of high atmospheric interest, such as IO or BrO, as needed for monitoring these species in the environment. We apply cavity-enhanced absorption spectroscopy in the near UV range using a frequency-doubled Ti:Sa mode-locked femtosecond laser. Efficient broadband injection of a high-finesse cavity is obtained by matching this optical frequency-comb source to the comb of cavity transmission resonances. A grating spectrograph and a detector array disperse and detect the spectrum transmitted by the cavity carrying the absorption features of intracavity molecules. Spectra recorded over ~4 nm with 10 s averaging display a noise level of 8 x 10(-10)/cm.
Méjean
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G
Laboratoire de Spectrométrie Physique, CNRS Unité Mixte de Recherche 5588, Université J Fourier de Grenoble, Saint Martin d'Hères, France.
Kassi
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S
Romanini
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D