Physical and Chemical Alterations of Ices by Fast Proton Irradiation, Particularly Ozone Synthesis
VIRGINIA UNIV CHARLOTTESVILLE SCHOOL OF ENGINEERING AND APPLIED SCIENCE
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In this thesis, we investigated the interaction of 100 keV protons with thin ice films grown under ultra-high vacuum conditions. We determined irradiation of pure water ice produced an upper limit of 0.04 O2proton that stayed within the film. Determination of this value came from thermally desorbing the films and measuring the O2 released with a quadrupole mass spectrometer. Irradiation of films of solid oxygen, carbon dioxide, hydrogen peroxide, and oxygenwater mixtures led to significant ozone 03 production. We quantified ozone production within the films using thermal desorption and ultraviolet reflectance techniques. Direct irradiation of pure water films did not yield any measurable ozone signal. We compared our results with recent astronomical observations of icy moons in the outer solar system. Molecular oxygen, created and trapped in water ice by 100 keV proton bombardment, seems insufficient to account for the oxygen absorption features in the visible spectrum discovered on Ganymede. Ozone produced from oxygenwater mixed-ice films generates a Hartley band in the ultraviolet similar in depth to those seen on Ganymede, Rhea, and Dione. The difference in laboratory band position compared with satellite band position suggests the need to revise assumptions concerning the surface ice.
- Atmospheric Physics
- Radiation and Nuclear Chemistry