LABORATORY MEASUREMENTS OF THE MICROWAVE PROPERTIES OF H2S UNDER SIMULATED JOVIAN CONDITIONS WITH AN APPLICATION TO NEPTUNE

H2S opacity may significantly affect the brightness temperatures of Uranus and Neptune due to possible depletion of ammonia in the tropospheres of those planets (de Pater et al. 1991, Icarus 91, 220-233). Though the rotational line centers of H2S are in the millimeter wavelength region, significant absorption is also present at centimeter wavelengths due to pressure broadening of the lines. Accordingly, the properties of H2S under Jovian conditions have been measured in order to constrain further the constituents' abundances on these planets. These absorptivity measurements show values that are significantly greater than values predicted by the Van Vleck-Weisskopf models traditionally used at centimeter wavelengths. In order to better model the opacity due to H2S under Jovian conditions a Ben-Reuven lineshape formalism has therefore been developed and is presented. This formalism provides a possible constraint on the relative abundances of H2S and NH3 on Neptune based on Voyager 2 radio occultation results (Lindal 1992, Astron. J. 103, 967-982). (C) 1994 Academic Press, Inc.