1. Faculty of Physics; University of Bialystok; Lipowa 41 15-424 Białystok Poland
2. Helmholtz Zentrum Dresden-Rossendorf; Dresden Germany
3. Technische Universitaet Dresden; Dresden Germany
4. Institute of Molecular Physics; Polish Academy of Sciences; M. Smoluchowskiego 17 60-179 Poznań Poland
5. Institute of Physics; Polish Academy of Sciences; Aleja Lotników 32/46 02-668 Warsaw Poland
6. Institute of Physics; ASCR; Na Slovance 2 18221 Prague 8 Czech Republic