1. Department of Physics “E.R. Caianiello”, University of Salerno, Via Giovanni Paolo II 132, Fisciano (Sa) 84084, Italy
2. Department of Chemistry and Industrial Chemistry, University of Pisa, Via Giuseppe Moruzzi 13, Pisa 56124, Italy
3. CNR, Institute for Plasma Science and Technology, Via Giovanni Amendola 122/d, Bari 70126, Italy
4. CNR-SPIN, Salerno Unit, Via Giovanni Paolo II 132, Fisciano (Sa) 84084, Italy