1. Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States
2. Institut für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstraße 12, 76131 Karlsruhe, Germany
3. Department of Chemistry, University of Helsinki, P.O. Box 55 (A. I. Virtanens plats 1), FIN-00014 Helsinki, Finland