1. Department for Molecular Theory and Spectroscopy, Max-Planck-Institut für Kohlenforschung (KOFO), Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
2. Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, Private Bag 102904, 0632 Auckland, New Zealand
3. Department of Chemistry, Washington State University, Pullman, Washington 99164, United States