CONTINUUM IN THE WINDOWS OF THE WATER-VAPOR SPECTRUM - ABSORPTION OF H2O-AR AT 239 GHZ AND LINEWIDTH CALCULATIONS

Absolute absorption rates of mixtures of water vapor and argon have be en measured at 239 GHz, which is an atmospheric window for the rotatio nal spectrum of water vapor. The dependence on pressure as well as tem perature has been obtained. The experimental data are compared with mo dels using conventional line profiles. As these models require the kno wledge of the collisional linewidths of H2O broadened by Ar, theoretic al calculations using the Robert-Bonamy formalism have been carried ou t. A continuum effect is observed when comparing the experimental abso rption with the models, as well as for the magnitude of the absorption discrepancy and for the strong temperature dependence of this absorpt ion. The effect, when compared to the collisional broadening efficienc y, is about the same as that observed for H2O-N-2. (C) 1998 Elsevier S cience Ltd. All rights reserved.