Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 32: Metal Substrates I
O 32.3: Vortrag
Dienstag, 12. März 2013, 11:00–11:15, H42
Electron pair emission from Ag(100) — •Lucie Behnke1, Frank O. Schumann1, and Jürgen Kirschner1,2 — 1Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle/Saale — 2Institut für Physik, Martin-Luther-Universität, D-06120 Halle/Saale
A recent (e,2e) study on a Cu(100) surface revealed the importance of pair diffraction. A kinematic pair diffraction model described the results reasonably well. The approach is justified by current (e,2e) theory, which characterizes the in-coming and out-going electrons by LEED and time reversed LEED-states, respectively. To explore the validity of the kinematic model, the experiment was repeated with a Ag(100) crystal. We have systematically studied the electron pair emission from the surface as a function of the primary energy (Ep = 30 eV to 67 eV). An improvement to the previous experiment is the ability to measure the primary electron flux. This allows to determine the single/coincidence count rate per incoming electron. In addition, we identify contributions from valence states of different orbital characters. The spectra can be divided into three regions with the help of a theoretical band structure calculation. We focus now on the region near Ef, which has a low DOS. However, in the experiment high intensities were measured. Moreover, the relative spectral contribution from the electrons near Ef is strongly affected by the primary electron energy and display a non-monotonic behavior. The origin of these variations and the similarities and differences with respect to the Cu(100) surface will be discussed.