Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Methods: Atomic and electronic structure

O 36.4: Vortrag

Dienstag, 23. März 2010, 15:45–16:00, H34

Characterization of the angular resolution of an inverse-photoemission experiment — •Anna Zumbülte, Kathrin Wulff, Anke B. Schmidt, and Markus Donath — Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

Inverse photoemission (IPE) is an experimental method to investigate the unoccupied part of the electronic structure above the Fermi level with k resolution within a wide range of the Brillouin zone. The setup consists of a detection system for photons and an electron gun, whose beam divergence determines the angular resolution of the IPE experiment. While the improvement of the energy resolution has been addressed before [1], the improvement of the angular resolution was often neglected so far.

We present a quantitative approach to investigate the electron-beam divergence based on angle-resolved IPE spectra for dispersing sp-derived surface states on Cu(111). The simulation of spectra with different beam divergences shows a strong sensitivity of the peak intensities on the angular resolution. We discuss different criteria, which can be used to evaluate the beam divergence by comparing the simulated with the measured spectra. We apply these criteria to spectra measured with a high-resolution electron gun and compare the results with beam-profile measurements.

[1] M. Budke et al., Rev. Sci. Instrum. 78, 113909 (2007)