CO2-broadening of water-vapor lines

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Journal of Molecular Spectroscopy




Measurements of CO2-broadened half-widths of 31 transitions belonging to the ?1, 2?2, and ?3 bands of water vapor were made at T = 294.4 K. Calculations following the formalism of Robert and Bonamy with an electrostatic and atom-atom interaction potential and dynamics correct to second order in time were performed for 562 transitions relevant to the 1- to 2.5-?m region. The calculations were compared with the measurements made in this work, a recent study by Langlois et al. (J. Mol. Spectrosc.167, 272-281, 1994), and an earlier work by Varanasi et al. (J. Quant. Spectrosc. Radiat. Transfer.11, 223-230, 1971). The calculations compared with experiment show average percent differences of +12, +1.5, and ?8, respectively, for the works listed above. Unfortunately there are no common lines measured by the different groups so a direct comparison of the measurements is not possible. Calculations of the temperature dependence of the halfwidths were made for 34 transitions. The temperature dependence of the half-widths determined from theory and the measurements of Langlois et al. agree reasonably well with two exceptions.