1. Institute of Physics, Bijenička cesta 46, 10 000 Zagreb, Croatia
2. Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia
3. IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
4. Institute of Applied Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland