1. Instituto de Tecnologia Química e Biológica-UNL, P-2781-901 Oeiras, Portugal, Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway, UCEH-Universidade do Algarve, P-8000−062 Faro, Portugal, and Instituto Superior Técnico-UTL, P-1049-001 Lisboa, Portugal