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O: Fachverband Oberflächenphysik

O 18: Poster Session I - MA 141/144 (Atomic Wires; Size-Selected Clusters; Nanostructures; Metal Substrates: Clean Surfaces+Adsorption of Organic / Bio Molecules+Solid-Liquid Interfaces+Adsorption of O and/or H; Surface or Interface Magnetism; Oxides and Insulators: Clean Surfaces)

O 18.56: Poster

Montag, 25. Februar 2008, 18:30–19:30, Poster F

Deviation from pure s-wave scattering of surface-state electrons from adatoms — •Tobias Sonnleitner and Jascha Repp — Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg

Surface state electrons on the close-packed surfaces of noble metals form a two-dimensional nearly-free electron gas. The scattering of the electrons off adatoms generates standing wave patterns in the electron density, which can be directly observed with the scanning tunneling microscope. Analysis of the standing wave patterns provides a direct way to determine the scattering properties of the adatoms. So far it has been widely accepted that metal adatoms act as s-wave scatterers due to the efficient screening of the adatom potential by bulk electrons. However, a deviation from a pure s-wave scattering would only express itself in the fraction of the standing wave pattern arising from multiple scattering events. This fraction is rather small since adatoms act as ideal absorbing black scatterers. Therefore, it is not obvious from the experimental point of view, that the assumption of a pure s-wave scattering is justified. To this end we have studied isolated pairs of copper adatoms on a clean Cu(111) substrate surface. The standing-wave patterns around these pairs have been analyzed in numerous different arrangements in order to average out effects from other scattering centers far away. In comparison to calculated patterns the fraction of these patterns arising from multiple scattering events has been extracted.