NEW CALCULATIONS AND HIGH-TEMPERATURE MEASUREMENTS OF $H_{2}O$ COLLISIONAL-BROADENING

Abstract

$^{1}$ B. Labani, J. Bonamy, D. Robert, J. M. Hartmann, and J. Taine, in press at J. Chem. Phys. Address of Hartmann and Taine: Labortioire d'Energ\'{e}tique Mol\'{e}culaire et Macroscopique, Combustion, Ecole Centralc des Arts et Manufactures, Grande voie des vignes, 92295 Chatenay-Malabry, France. Address of Bonamy, Labani and Robert: Laboratoire de Physique mol\'{e}culaire, Facult\'{e} des Sciences et Techniques. 25030 Besan\'con Cedex, France.Author Institution:Comparisons between available room temperature infrared experimental $H_{2}O$ line-widths and results of a recent semi-classical $model^{1}$ developped by the authors are presented. The latter, contrarily to these generally used up to now for $H_{2}O$ collisional-broadening, provides a satisfactory treatment of close collisions through modelings of both trajectory modifications and short-range potential contributions; these improvements are demonstrated by the accurate results obtained for $N_{2}$-broadening of high rotational quantum number lines and for the broadenings associated to weakly $(O_{2})$ or non-polar (Ar) perturbers. Accurate diode-laser measurements of $H_{2}O$ infrared line-parameters in the 400-900 K temperature range are also presented. The measured self- and $N_{2}$-broadened widths of some high rotational quantum number lines show unusually slow decreasings with temperature. Detailed analysis of the data demonstrates the great influence of a ``resonance overtaking'' mechanism. The latter is well accounted for by our model and results from the modifications of both the velocities and perturber revibrational populations distributions with temperature