1. Department of Chemistry and Molecular Biology, University of Gothenburg, 412 96 Göteborg, Sweden
2. Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
3. Department of Applied Physics and Science Education, Eindhoven Hendrik Casimir Institute and Institute for Complex Molecular Systems, Eindhoven University of Technology, 5612 AE Eindhoven, The Netherlands