1. Department of Chemistry; Philipps-Universität Marburg; Hans-Meerwein-Str. 4 35032 Marburg Germany
2. Centre for Theoretical Chemistry and Physics; The New Zealand Institute for Advanced Study and the Institute for Natural and Mathematical Sciences; Massey University; Albany New Zealand
3. Molecular Theory and Spectroscopy; Max-Planck-Institut für Kohlenforschung; 45470 Mülheim an der Ruhr Germany