1. Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34−36, D-45470 Mülheim an der Ruhr, Germany
2. Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
3. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
4. Institute of Optics and Atomic Physics, Technical University of Berlin, Hardenbergstraße 36, D-10587 Berlin, Germany