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A by electron impact and its application to modeling the Jovian aurora have been carried out. Our laboratory data suggest that at 100 eV the relative cross sections for direct excitation of Lya, Lyman bands (B 1~u +-x 1~/), and Werner bands (C 1 '1Tu-X 1~/) are 1, 2.3±0.6, and 2.6±0.5, respectively, in conflict with Stone and Zipfs (1972) results for the Werner bands. Cascade from E, F 1~g + states contributes an additional 31% to the B 1~u + state population. It is shown that the most likely fate for the metastable H(2 2 S) atoms produced in the Jovian aurora is collisional quenching to H(2 2 P), and this could add as much as 60% to the predicted Lya emission. On the basis of detailed atmospheric and radiative transfer modeling, we conclude that the recent JUE and Voyager observations are consistent with precipitation of electrons with energy in the range of 1-30 keV or other energetic particles that penetrate to number densities of 4 X 10 10-5 X 10 13 cm-3 or column densities of 5 X 10 17-2 X 10 20 cm-2 in the atmosphere. The globally averaged energy flux and production of hydrogen atoms are 0.5-2 ergs cm-2 s-1 and 1-4 X 10 10 atoms cm-2 s-1, respectively.

Utilizing a crossed electron beam and a molecular beam collision geometry and the single particle counting technique, cross sections for the production of positive ions by electron impact on methanol have been measured for electron impact energies ranging from 0 to 500 eV. Appearance potentials for the various ionic fragments have also been obtained. These potentials are compared with values calculatedfrom the heats of formation for methanol and for neutral and cationic products in order to identify the various channels of dissociation at threshold energies. Introductionbeam of electrons which is collimated by a magnetic field of about 100 G. This beam of electrons crosses a beam of mole-Recently, there has been a great interest in the electron impact cules, which is generated by flowing the gas under study ionization properties of organic molecules because of their dis-through a capillary array. Collisions of electrons with the molecovery in the planetary [Keating et a/.,1987] (Jupiter and Saturn) cules in the beam generate cations. They are extracted out of and cometary [Kissel and Kruger, 1995 ] atmospheres and inter-the collision region by a pair of wire meshes by applying an stellar space f e.g., polycyclic aromatic hydrocarbons electric field which is perpendicular to both the electron beam [Allamandola. 1992] and also because of their use in combustion and the molecular beam. Since the electric field can disturb the as alternative fuels and in the semiconductor industry, e.g., dia-beam of electrons, a pulsing scheme is employed where both mond film deposition [Ikeda et al., 1995]. Collisions of electrons the electron beam and the electric field are pulsed. The pulsing with organic molecules generate a variety of radicals which are sequence is such that when the pulse of electrons interacts with chemically very active. For example, CH3OH dissociates into 15 the molecular beam, the electric field for extracting the ions is cations and each dissociative cham•el gives rise to several neutral zero. However, the extraction field of about 50 V/cm is applied radical species. However, cross sections for their production from right after the electron pulse. Such a large field ensures a com-CH3OH for different electron impact energies have never been plete collection of all cations irrespetive of the kinetic energies published. The only previously published data on this molecule (<5 eV) with which they are born. are by Djuric et al. [1989], who measured cross sections for theThe extracted ions are focused at the entrance of a quadproduction of all cations (i.e., total ionization cross sections) for rupole mass spectrometer (QMS) by the help of electrostatic an electron impact energy range of 0 to 300 eV. A detailed study lenses. The QMS selects the various cations. The cations are of the various channels of dissociation and kinetic energies of the detected by a charged particle detector, which was a channelfragment ions has never been performed. This motivated us to tron for these measurements. Each detected charged ...

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