1 CFisUC, Department of Physics, University of Coimbra, Rua Larga, P-3004-516 Coimbra, Portugal.
2 CQC, Department of Chemistry, University of Coimbra, Rua Larga, P-3004-535 Coimbra, Portugal.
3 CFisUC, Department of Physics, University of Coimbra, Rua Larga, P-3004-516 Coimbra, Portugal; Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstrasse 4, 80799 München, Germany.
4 CFisUC, Department of Physics, University of Coimbra, Rua Larga, P-3004-516 Coimbra, Portugal; Higher Polytechnic School of Huesca, University of Zaragoza, Carretera de Cuarte s/n, 22071 Huesca, Spain. Electronic address: pmr@unizar.es.
5 Advanced Materials Laboratory, ETSIIAA, Universidad de Valladolid, Avda. Madrid 44, 34004 Palencia, Spain.
6 CFisUC, Department of Physics, University of Coimbra, Rua Larga, P-3004-516 Coimbra, Portugal. Electronic address: manuela@pollux.fis.uc.pt.