1. Department of Engineering Sciences and Mathematics, Division of Materials Science, Applied Physics, Luleå University of Technology, 971 87 Luleå, Sweden
2. Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 405 30 Gothenburg, Sweden
3. Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic