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. Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
4. IBM Research−Zurich, Science and Technology Department, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland