Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)

O 36.1: Poster

Dienstag, 15. März 2011, 18:30–22:00, P4

Electron pair emission from a Cu(111) surface — Rajendra S. Dhaka, •Frank O. Schumann, Grant A. van Riessen, Zheng Wei, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany

We aim to explore the validity of an important assumption of the theoretical description of the (e,2e) process, namely an effective single electron description of the electronic properties of the sample. If affirmative the orbital character of the valence state can be identified and it would be of interest to find conditions where the emission is dominated by a particular valence state. In order to test the conjecture we selected a Cu(111) surface as sample which has a well-known electronic structure. We varied the primary energy in the range 19-65 eV. The sum energy spectra reveal features which can be directly related to the effective single particle band structure of the sample. This proves that for Cu an effective single particle picture is an adequate description within a (e,2e) experiment. The relative pair emission intensity from the surface state and 3d states is observed to vary dramatically with the primary energy. At low excitation energies the spectrum is dominated by the contribution from the Shockley surface state. We propose a simplified model based on the diffraction of pairs to explain this observation.