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J. E. Allen, Jr. (NASA GSFC), R. N. Nelson (GASoU/NASA GSFC)
Light hydrocarbons play important roles in the development of atmospheres, clouds, and hazes in the outer planets and some of their satellites. The first-order equilibrium and photochemical models developed to describe these systems require accurate laboratory data as inputs. It is important that these data are acquired over the appropriate range of atmospheric parameters, e.g., temperature, and in this regard there is a particular need for vapor pressures of molecular constituents at low temperatures. We have developed an apparatus capable of providing this extremely limited information and have undertaken a program to systematically determine the thermodynamic properties of molecules and mixtures of importance to the planetary atmospheres community. Previously we reported results for ethylene and propane (Nelson, Allen, and Harris 1997) and methane and monodeuterated methane (Allen and Nelson 1998). In our continuing efforts to supply these needed data, we update our list of low-temperature vapor pressures for light hydrocarbons by reporting here the experimentally determined vapor pressure of acetylene from 0.3 to 8x10-6 torr, corresponding to temperatures from 124 to 84 K, respectively. This extends the available measured data for this molecule by over two orders of magnitude in pressure.
\noindent \\ Nelson, R. N., Allen, J. E., Jr., and Harris, B. C., Sr. 1997, B.A.A.S. {bf 29}, 1009. \noindent Allen, J. E., Jr. and Nelson, R. N. 1998, to appear in Proc. of the NASA Laboratory Space Science Workshop (Cambridge: Harvard-Smithsonian).
\noindent \\ RNN is a summer faculty researcher from the Department of Chemistry, Georgia Southern University.
The author(s) of this abstract have provided an email address for comments about the abstract: john.e.allen@gsfc.nasa.gov