[1] INFN Lab Nazl Frascati, Via Enr Fermi, I-00044 Frascati, Italy
[2] INFN Sez Lecce, Via Arnesano, I-73100 Lecce, Italy
[3] Univ Salento, Dept Phys, Via Arnesano, I-73100 Lecce, Italy
[4] Univ Milano Bicocca, Dept Phys, Piazza Sci, I-20126 Milan, Italy
[5] INFN Milano Bicocca, Piazza Sci, I-20126 Milan, Italy
[6] Univ Salerno, Dept Phys, Via Giovanni Paolo 2, I-84084 Fisciano, Salerno, Italy
[7] INFN Napoli, Salerno Grp, Via Giovanni Paolo 2, I-84084 Fisciano, Salerno, Italy
[8] Univ Sannio, Dept Sci & Technol, Via Francesco Sanctis, I-82100 Benevento, Italy
[9] Univ Sannio, Dept Engn, Corso Garibaldi, I-82100 Benevento, Italy
[10] INO CNR BEC Ctr, Via Sommar, I-38123 Povo, Italy
[11] Univ Trento, Dept Phys, Via Sommar, I-38123 Trento, Italy
[12] Fdn Bruno Kessler, Via Sommar, I-38123 Trento, Italy
[13] INFN TIFPA, Via Sommar, I-38123 Trento, Italy
[14] IFN CNR, Via Sommar, I-38123 Trento, Italy
[15] INRiM Ist Nazl Ric Metrolog, Str Cacce, I-10135 Turin, Italy
[16] Politecn Torino, Corso Duca Abruzzi, I-10129 Turin, Italy
[17] INFN Torino, Via Pietro Giuria, I-10125 Turin, Italy
[18] Ist Nanosci, Natl Enterprise Nanosci & Technol NEST, CNR, Pisa, Italy
[19] Scuola Normale Super Pisa, Pisa, Italy