1. Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań, Poland
2. A. Chełkowski Institute of Physics, Silesian University, Uniwersytecka 4, 40-007 Katowice, Poland
3. W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław, Poland