1. Department of Chemistry-Ångström, Physical Chemistry Division, Uppsala University, Uppsala 751 20, Sweden
2. Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, Gothenburg 412 58, Sweden
3. Department of Chemistry-Ångström, Structural Chemistry Division, Uppsala University, Uppsala 751 20, Sweden
4. Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw 01-224, Poland