1. Institute of Experimental Physics, SAS, Watsonova 47, 040 01 Košice, Slovakia
2. Institute of Chemistry, P.J. Šafárik University, Moyzesova 11, 041 54 Košice, Slovakia
3. Institute of Mathematics, Physics and Mechanics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
4. BENSC - Helmholtz-Zentrum, Glienicker Str. 100, 141 09 Berlin, Germany