1. Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
2. Department of Physics, Technische Universität Kaiserslautern, Erwin-Schroedinger-Str. 46, D-67663 Kaiserslautern, Germany
3. Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark