1. Department
of Chemistry and Biochemistry, University of Bern, Freiestrasse
3, CH-3012 Bern, Switzerland
2. Physics
Institute, Space Research and Planetary Sciences, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
3. IBM Research - Zurich, Science and Technology
Department, Säumerstrasse
4, CH-8803 Rüschlikon, Switzerland