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Peter L. Smith (Harvard-Smithsonian CfA), G. Stark (Wellesley College), J. Rufus, J. C. Pickering, G. Cox (Imperial College, London), K. P. Huber (NRC, Canada)
The determination of the chemical composition of the atmosphere of Io from Hubble Space Telescope observations in the 190-220~nm wavelength region requires knowledge of the photoabsorption cross sections of SO2 at temperatures ranging from about 110~K to 300~K. We are engaged in a laboratory program to measure SO2 absorption cross sections with very high resolving power (\lambda/\delta\lambda ~q 450,000) and at a range of temperatures appropriate to the Io atmosphere. Previous photoabsorption measurements, with \lambda/\delta\lambda ~q 100,000, have been unable to resolve the very congested SO2 spectrum, and, thus, to elucidate the temperature dependence of the cross sections. Our measurements are being performed at Imperial College, London, using an ultraviolet Fourier transform spectrometer. We will present our recently completed room temperature measurements of SO2 cross sections in the 190-220~nm region and plans for extending these to ~195~K.
Analyses of Voyager VUV occultation measurements of the N2-rich atmospheres of Titan and Triton have been hampered by the lack of fundamental spectroscopic data for N2, in particular, by the lack of reliable f-values and line widths for electronic bands of N2 in the 80-100~nm wavelength region. We are continuing our program of measurements of band oscillator strengths for the many (approximately 100) N2 bands between 80 and 100~nm. We report new f-values, derived from data obtained at the Photon Factory (Tsukuba, Japan) synchrotron radiation facility with \lambda/\delta\lambda ~q130,000, of 37 bands in the 80-86~nm region and 21 bands in the 90-95~nm region. We have also begun the compilation of a searchable archive of N2 data on the World Wide Web; see http://cfa-www.harvard. edu/amp/data/n2/n2home.html. The archive, covering the spectroscopy of N2 between 80 and 100~nm, will include published and unpublished 14N2, 14N15N, and 15N2 line lists and spectroscopic identifications, excited state energy levels, band and line f-values, a summary of published band f-value and line width measurements, and a cross-referenced summary of the relevant N2 literature.
The author(s) of this abstract have provided an email address for comments about the abstract: plsmith@cfa.harvard.edu