Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 46: Time-resolved spectroscopies I

O 46.10: Vortrag

Donnerstag, 26. März 2009, 12:45–13:00, SCH A315

Correlated positron-electron emission from surfaces — •Frank O. Schumann, Grant van Riessen, Michael Birke, Carsten Winkler, and Jürgen Kirschner — Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle

Electrons in a solid do not move independent from each other. The Pauli principle demands that two electrons with parallel spins can not be at the same location. The Coulomb interaction makes it energetically unfavorable for electrons to be close to each other. This constitutes the concept of the exchange-correlation (xc) hole. Our electron pair emission studies demonstrate that this concept is an experimental reality. In these experiments a primary electron or photon hits a surface and emits an electron pair. In order to disentangle the different contributions to the xc-hole, one should use as primary particle a positron and study the positron-electron pair emission. In this case one does not need to consider the Pauli principle. Because of this motivation we performed the first experiment, which demonstrates that the impact of a positron causes indeed the emission of a positron-electron pair. We used the NEPOMUC facility together with a pair of hemispherical analyzers operated with a coincidence circuit. As target we selected a LiF(100) surface, which was hit with 85 eV primary positrons. We find that the emission of positron-electron pairs is time correlated.