1. Hylleraas Centre for Quantum Molecular Sciences Dpt. of Chemistry University of Oslo P.O. Box 1033 Blindern 0315 Oslo Norway
2. Former address Dpt. of Chemistry Aarhus Universitet Langelandsgade 140 8000 Aarhus C Denmark
3. Fachbereich Chemie and Forschungszentrum OPTIMAS Technische Universität Kaiserslautern Erwin-Schrödinger-Straße 67663 Kaiserslautern Germany
4. Institute of Nanotechnology Karlsruhe Institute of Technology (KIT) Postfach 3630 76021 Karlsruhe Germany