Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008dps....40.5409d&link_type=abstract
American Astronomical Society, DPS meeting #40, #54.09; Bulletin of the American Astronomical Society, Vol. 40, p.497
Astronomy and Astrophysics
Astronomy
Scientific paper
A new laboratory system capable of measuring the millimeter-wave properties of gases between 2 and 4 mm has been developed at Georgia Tech. A times-six active multiplier chain and/or a frequency tripler are used to generate the high frequency signals and various harmonic mixers are used with a spectrum analyzer for detecting the signals. The millimeter-wave continuum opacity of ammonia has been measured using a fully confocal Fabry-Perot resonator enclosed in a glass tube capable of withstanding 3 bars of pressure. Measurements are presented of the opacity and refractivity of ammonia gas mixture (hydrogen 85%, helium 13%, and ammonia 2-4%) in the 2-3 mm range and pure ammonia in the 2-4 mm range at room temperature and pressures between 0.02 and 3 bars.
To date, only a very limited number of measurements of the opacity of ammonia have been made in the millimeter-wave range and none of these measurements give an insight into effects of the ammonia rotational spectrum on the frequency dependence of the opacity. Measurements of the hydrogen and helium broadened millimeter-wave opacity of ammonia under simulated Jovian atmospheric conditions will help to better interpret the mmw-emission spectrum of those planets and will also help predict the potential effects of the rotational lines on the centimeter-wave emission from the deepest levels of those atmospheres. The ammonia opacity measurements may also provide insight into the behavior of the 140 GHz transition in the v2 vibrational band of ammonia (Shimizu, J. Chem. Phy., 51, 1969).
This work is supported by the NASA Planetary Atmospheres Program under Grant NNG06GF34G.
Devaraj Kiruthika
Steffes Paul Gregory
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