Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5415767 | Journal of Molecular Spectroscopy | 2007 | 21 Pages |
Abstract
The CO2-broadened water coefficients (half-widths, line shifts, and temperature dependence of the widths) are predicted using a fully complex Robert-Bonamy formulation for the 937 allowed and forbidden perpendicular type transitions of (000)-(000) between 200 and 900 cmâ1 in order to facilitate atmospheric remote sensing of Mars and Venus. In addition, empirical Lorentz line widths and pressure-induced frequency-shifts of CO2-broadened H216O are obtained at room temperature for 257 perpendicular transitions of the (010)-(000) fundamental. For this, calibrated spectra recorded at 0.0054 cmâ1 resolution are measured assuming Voigt line shapes. For transitions between 1287 and 1988 cmâ1 with rotational quanta up to J = 13 and Ka = 6, the widths vary from 0.045 to 0.212 cmâ1 atmâ1 at 300 K; the pressure-shifts are quite large and range from â0.0386 to +0.0436 cmâ1 atmâ1. For the (010)-(000) band, the RMS and mean observed and calculated differences for CO2-broadened H2O half-widths are 12% and â1.9%, respectively, while the RMS and mean ratios of the observed and calculated pressure-induced shift coefficients are 1.6 and 0.79, respectively. For pairs of transitions involving Ka = 0 and 1, such as 20 2 â 31 3 and 31 3 â 20 2, both the calculated and observed pressure induced shifts in positions are opposite in sign and often similar in magnitude. The data are too limited to characterize vibrational dependencies of the widths, however.
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Physical and Theoretical Chemistry
Authors
L.R. Brown, C.M. Humphrey, R.R. Gamache,