1. Contribution from the Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, DK-4000, Roskilde, Denmark, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Copenhagen, Denmark, Department of Chemistry and NanoDTU, Building 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark, and Department of Physics and Astronomy, University of Århus, DK-8000, Århus C, Denmark