1. Department of Physics, University of Konstanz, 78457 Konstanz, Germany
2. Institut für Theoretische
Festkörperphysik and DFG Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76128 Karlsruhe,
Germany
3. Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
4. Helmholtz-Zentrum Dresden Rossendorf, 01328 Dresden, Germany