1. Physics Department, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
2. Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
3. Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám 2, CZ-16610 Prague 6, Czech Republic