1. Department of Physics (E20), Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
2. Department of Chemistry, Chair of Theoretical Chemistry, Technische Universität München, Lichtenbergstraße 4, 85748 Garching, Germany
3. Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, 1015 Lausanne, Switzerland