1. Department of Physics, University of Ioannina, 451 10 Ioannina, Greece; Biomedical Research Institute, Foundation for Research and Technology-Hellas, P.O. Box 1186, 451 10 Ioannina, Greece; Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1527, 711 10 Heraklion Crete, Greece; Department of Physics, University of Crete, 710 03 Heraklion Crete, Greece; and Department of Chemical Engineering, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece