1. Institut für Physikalische Chemie; Heinrich-Heine-Universität Düsseldorf; Universitätstr. 1 40225 Düsseldorf Germany
2. Current address: Department of Chemistry; The Ohio State University; 100 West 18th Avenue Columbus OH 43210 USA
3. Department of Physics; Durham University; Durham DH1 3LE United Kingdom
4. Faculty of Chemistry; Silesian University of Technology; M. Strzody 9 44-100 Gliwice Poland