1. Department of Chemical Engineering and Materials Science and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Theoretische Chemie, Universität Heidelberg, INF 229, D-69120 Heidelberg, Germany
3. National Institute of Lasers, Plasma and Radiation Physics, Institute of Space Science, POB MG-23, RO 077125 Bucharest, Romania