1. Department of Physics, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece
2. Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografrou, 15771 Athens, Greece
3. Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O.
Box 1385, Heraklion, 711 10 Crete, Greece