1. National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG-36, RO 76900, Bucharest-Magurele, Romania, University of Bucharest, Department of Chemical Technology and Catalysis 4-12 Regina Elisabeta Boulevard, Bucharest 030016, Romania, Institute of Chemistry, Physical Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany, and Babes-Bolyai University, Faculty of Physics, Institute for Interdisciplinary Experimental Research, 400084 Cluj-Napoca, Romania