Collisions rasantes d'ions ou d'atomes sur les surfaces : de l'échange de charge à la diffraction atomique

Abstract : This Ph.D. memoir reports two studies of the interaction with insulating surfaces of keV ions or atoms
under grazing incidence.
The first part presents a study of charge exchange processes occurring during the interaction of singly charged ions with the surface of NaCl. In particular, by measuring the scattered charge fraction and the energy loss in coincidence with electron emission, the neutralization mechanism is determined for S^+, C^+, Xe^+, H^+, O^+, Kr^+, N^+, Ar^+, F^+, Ne^+ and He^+. These results show the importance of the doubleelectron capture as neutralization process for ions having too much potential energy for resonant capture and not enough for an Auger neutralization. We have also studied the ionisation of the projectile and of the surface, and the different Auger-like neutralization processes resulting in electron emission, population
of conduction band or excited state. For oxygen scattering, we have measured an higher electron yield in coincidence with scattered negative ion than with scattered atom suggesting the transient formation above the surface of the oxygen doubly negative ion.
The second study deals with the fast atom diffraction, a new phenomenon observed for the first time during this work. Due to the large parallel velocity, the surface appears as a corrugated wall where rows interfere. Similarly to the Thermal Atom Scattering the diffraction pattern corresponds to the surface potential and is sensitive to vibrations. We have study the H–NaCl and He–LiF atom-surface potentials in the 20 meV–1 eV range. This new method offers interesting perspectives for surface characerisation.
Document type :
Theses
Atomic Physics. Université Paris Sud - Paris XI, 2006. French


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Submitted on : Monday, October 16, 2006 - 10:41:25 AM
Last modification on : Monday, October 16, 2006 - 12:21:19 PM

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Patrick Rousseau. Collisions rasantes d'ions ou d'atomes sur les surfaces : de l'échange de charge à la diffraction atomique. Atomic Physics. Université Paris Sud - Paris XI, 2006. French. <tel-00106727>

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