We investigated the electron impact-induced fluorescence spectrum of SO2 to provide excitation cross sections for modeling Io's emission spectrum and analyzing Cassini Imaging Science Subsystem observations. The electron-excited middle-ultraviolet visible optical near-infrared (VOIR) emission spectrum Of SO2 gas was geperated in the laboratory and studied from 2000 to 11,000 A?? at a resolution of ???? ???2.5 A?? full width at half maximum (FWHM). The VOIR laboratory spectrum longward of 6000 A?? consists entirely of S I, II and O I, II multiplets for electron impact energies above ???15 eV. Between 2000 and 6000 A??, we find previously identified molecular bands from both SO and SO2. This work represents a significant improvement in spectral resolution over our earlier work done at 18 A?? FWHM. From a measurement of the medium-resolution spectrurn, we provide qetailed 25- and 100-eV emission cross sections for spectral features from 2000 to 11,000 A??. On the basis of these data, we suggest future ground-based and satellite telescopic observations in the VOIR that are of promise for understanding Io's atmosphere. Copyright 2008 by the American Geophysical Union.
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Middle UV to near-IR spectrum of electron-excited SO2