Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 8: Posters Thursday: Dissociation and other Collision Processes
MO 8.25: Poster
Donnerstag, 5. April 2001, 12:30–15:00, AT3
Formation and Evolution of Negative Ion Resonances in Condensed Ozone — •Petra Tegeder1, Martin Penno2, Paul A. Kendall1, Nigel J. Mason1, and Eugen Illenberger2 — 1University College London, Department of Physics and Astronomy, Gower Street, London WC1 6BT, UK — 2Freie Universität Berlin, Institut für Chemie-Physikalische und Theoretische Chemie, Takustr. 3, D-14195 Berlin, Germany
Electron stimulated desorption (ESD) of anions from multilayer films of
ozone deposited on a cryogenically cooled Au surface
under UHV conditions is studied in the energy range between 0 and 15 eV.
An intense desorption of the O− fragment ion is
observed in the energy range below 7 eV via three resonances and via a
comparatively broader feature around 10 eV.
Desorption of O2− occurs within a week resonance located at 7 eV
. The resonant behaviour of the electron
stimulated desorption below 8 eV indicates that the process is driven by
a direct dissociative electron attachment (DA) to ozone
molecules at or near the surface. The ESD results are compared with the
corresponding dissociative electron attachment processes
in the gas phase demonstrating the strong influence of the condensed
phase environment on the generation and evolution of
negative ions.
Implication for the heterogeneous chemistry of ozone on polar
stratospheric clouds particles, namely photoinduced dissociative
electron transfer from the substrate, are discussed in the light of the
high cross section for ESD.