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Berlin 2001 – scientific programme

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MO: Molekülphysik

MO 8: Posters Thursday: Dissociation and other Collision Processes

MO 8.25: Poster

Thursday, April 5, 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 Illenberger21University 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.

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