High sensitivity spectroscopy of the O2 band at 1.27 µm: (II) Air-broadened line profile parameters
Résumé
A cavity ring down spectrometer referenced to a frequency comb is used to study the profile of air-broadened O2 lines of the 1.27 µm band. To this aim, spectra of O2 in dry air and of O2 in N2 with 2% of O2 were measured, respectively in the 7720-7920 cm−1 and 7868-7887 cm-1 spectral ranges at room temperature and various pressures ranging from 50 to 700 Torr. Detailed line profile analysis is reported for 85 transitions using the speed dependent Nelkin-Ghatak model and a multi-spectrum treatment of the two series of spectra. Line mixing was found necessary to be taken into account in the analysis of lines in the region of the Q branch. The derived line parameters including the broadening and shifting coefficients, the speed dependent components of the collisional line broadening and shifting, as well as the Dicke narrowing parameter are discussed and compared to literature data. In particular, the speed dependence components of the collisional broadening are found to agree satisfactorily with predictions obtained by molecular dynamic simulations. This obtained set of line-shape parameters should allow for improved modeling of atmospheric spectra in the 1.27 um spectral region.
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