1. Contribution from the Department of Inorganic Chemistry 1, University of Bielefeld, P.O. Box 100 131, D-33501 Bielefeld, Germany, Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011-3160, Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam, Germany, Institute for Physical Chemistry, University of Hamburg, D-20146 Hamburg, Germany, Institut für Festkörperforschung (IFF), Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany, and Institute of...