1. Department of Chemistry, Clarkson University, Potsdam, New York 13699-5814, and Swiss Federal Institute of Technology, ETHZ-ITO, Grabenstrasse 3, 8952 Schlieren, Switzerland, and Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, 2300 RA Leiden, The Netherlands, and Physics Department, University of Fribourg, CH-1700 Fribourg, Switzerland