* Corresponding authors

^a Kekulé-Institut für Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, Bonn, Germany
E-mail: hoeger@uni-bonn.de

^b Department of Physics and Astronomy, University of Utah, Salt Lake City, UT, USA
E-mail: lupton@physics.utah.edu

^c Department of Materials Science, University of Utah, Salt Lake City, UT, USA
E-mail: lupton@eng.utah.edu

^d Theoretical Division and Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory (LANL), Los Alamos, NM, USA

^e Department of Chemistry, Laboratory of Photochemistry and Spectroscopy, and Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200-F, Leuven, Belgium
E-mail: Steven.DeFeyter@chem.kuleuven.be

^f Universität Hamburg, Institut für Physikalische Chemie, Grindelallee 117, Hamburg, Germany
E-mail: forster@chemie.uni-hamburg.de