$CO_{2}$-BROADENING OF WATER-VAPOR LINES

Abstract

Measurements of $CO_{2}$-broadened halfwidths of 31 transitions belonging to the $\nu_{1}, 2\nu_{2}$, and $\nu_{3}$ 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 done for 562 transitions relevant to the $1-2.5\mu$m region. The calculations were compared with the measurements made in this work, a recent study by Langlois et al. (J. Mol. Spectrosc. in press 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 halfwidths determined from theory and the measurements of Langlois et al. agree reasonably well with two exceptions.