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Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 19: Clean surfaces I

O 19.1: Talk

Monday, March 26, 2012, 17:30–17:45, A 053

Electron coincidence studies from S-overlayers on Cu(100) and Ni(100) — •Changhui Li1, Swapnil Patil1, Zheng Wei1, Lucie Behnke1, Frank O. Schumann1, Gianluca di Filippo2, Giovanni Stefani2, and Jürgen Kirschner11Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120Halle — 2Dipartimento di Fisica, Università Roma Tre,Rome, Italy

In a previous double photoemission study of a Cu(100) surface we proved that the Auger process proceeds via a single step rather than a two-step process. The evidence was the emergence of a diagonal line in the 2D-Energy spectrum in the coincidence experiment [1]. In related coincidence measurements on atomic targets diagonal lines in the 2D-Energy distributions are reported in the literature. In order to bridge the gap between solids and atomic targets we prepared S-layers on a solid surface. We exposed a Cu(100), a oxygen passivated Cu(100) and a Ni(100) surface to H2S gas. This caused the formation of S overlayers with nominal coverages of 0.25, 0.48 and 0.5 ML. We excited these structures with circular polarized light. The photon energy was adjusted such that the S 2p photoelectron and related Auger electron were both in the energy window of our coincidence spectrometer. We do not find a continuous energy sharing between photoelectron and Auger electron. Furthermore, we did not observe a helicity dependence of the coincidence and singles spectra. This means that the Auger emission from S proceeds via a two-step process.

[1] G. van Riessen, Z. Wei, R. S Dhaka, C. Winkler, F.O. Schumann, and J. Kirschner, J. Phys.: Condens. Matter 22, 092201 (2010).
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