1. Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova, Italy
2. Faculty of Humanities and Natural Sciences, University of Prešov, 17 Novembra 1, 080 01 Prešov, Slovakia
3. Institute of Experimental Physics, Slovak Academy of Science, Watsonova 47, 040 01 Košice, Slovakia
4. Department of Physics, CAB-CNEA, CONICET, IB-UNCuyo, 8400 S. C. de Bariloche, Argentina