ABSORPTION OF A H2O-CO2 MIXTURE IN THE ATMOSPHERIC WINDOW AT 239 GHZ - H2O-CO2 LINEWIDTHS AND CONTINUUM

Absolute absorption rates of mixtures of water vapor and carbon dioxid e have been measured at 239 GHz which is in an atmospheric window for the rotational and vibrational spectra of both species. The dependence on pressure as well as temperature has been obtained. The experimenta l data are compared with models using conventional lineshapes. As thes e models require the knowledge of the collisional linewidths of the H2 O broadened by CO2, theoretical calculations using the Robert-Bonamy f ormalism have been carried out. A very large ''continuum effect'' is o bserved when comparing the experimental absorption with the models, as well for the magnitude of the absorption discrepancy and for the stro ng temperature dependence of this absorption. Collision induced absorp tion (CIA) has also been measured at this frequency. These results can be applied to planetary observations. (C) 1996 Academic Press, Inc.