1. Institut für
Anorganische Chemie, Karlsruhe Institute of Technology, Engesserstrasse
15, D-76131 Karlsruhe, Germany
2. Department of Physics, University of Liège, B-4000 Sart-Tilman, Belgium
3. Department of Chemistry, Missouri University of Science
and Technology, University of Missouri, Rolla, Missouri 65409-0010, United States