1. Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4, A-8010 Graz, Austria; Department of Chemistry, Physical Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland; Ciba Specialty Chemicals Inc., 4002 Basel, Switzerland; and Institute of Experimental Physics, Free University of Berlin, Arnimallee 14, 14195 Berlin, Germany