[1] Univ Salerno, Dipartimento Fis ER Caianiello, I-84084 Fisciano, Sa, Italy
[2] Univ Salerno, Ctr Interdipartimentale Ric NANOMATES, I-84084 Fisciano, Sa, Italy
[3] Georgetown Univ, Dept Phys, Washington, DC 20057 USA
[4] Univ Salerno, Dipartimento Ingn Chim & Alimentare, I-84084 Fisciano, Sa, Italy
[5] CNR SPIN Salerno, I-84084 Fisciano, Sa, Italy