CO₂ Pressure Shift and Broadening of Water Lines Near 790 nm

Carbon dioxide pressure-broadened ro-vibrational transitions belonging to the v₂+3v₃ band of H₂¹⁶O have been measured with a sensitive cavity ring-down spectrometer. Water vapor of relatively low pressures (<0.5 Torr) was used to limit the self-collisions among water molecules. After the calibration using the precise atomic transitions of Rb and a thermostabilized Fabry-Pérot interferometer, 10⁻⁵ cm⁻¹ frequency accuracy has been achieved. Line parameters are derived from least-squares fitting of the spectra using the “soft” collision model. The retrieved line parameters can be applied in the study of water absorption in the CO₂-rich atmospheres of planets like Venus and Mars.