1. Faculty of Physics, “Alexandru Ioan Cuza” University, 11 Carol I Blvd., 700506 Iasi, Romania
2. Department of Physics, “Gh. Asachi” Technical University, 59A Mangeron Blvd., 700050 Iasi, Romania
3. Institute for Ion Physics and Applied Physics, University of Innsbruck, 25 Technikerstr., A-6020 Innsbruck, Austria