1. Centre Européen de Calcul Atomique et Moléculaire (CECAM), Ecole Normale Supérieure, 46 Allée d'Italie, 69007 Lyon, France, Hamburg University of Technology, Chemical Reaction Engineering, Eissendorfer Str. 38, D-21073 Hamburg, Germany, and Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.