1. Nuclear Physics Institute of the Czech Academy of Sciences, v. v. i.; Rez 250 68 Czech Republic
2. Department of Physics, Faculty of Science; J. E. Purkinje University; Ceske Mladeze 8 Usti nad Labem 400 96 Czech Republic
3. Department of Inorganic Chemistry; Institute of Chemical Technology; Prague 166 28 Czech Republic
4. Institute of Ion Beam Physics and Materials Research; Helmholtz Zentrum Dresden-Rossendorf; Dresden 01328 Germany