1. Institute of Physics, University of Zielona Góra, ul. Prof. Szafrana 4a, 65-516 Zielona Góra, Poland
2. Institute of Low Temp. & Struct. Research, Polish Academy of Sciences, ul. Okólna 2, 50-422 Wrocław, Poland
3. Faculty of Physics, A. Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland
4. School of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK