1. Institute of Nuclear Sciences “Vinča,” University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia
2. Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH), N. Plastira 100, Vassilika Vouton, 70013 Heraklion, Crete, Greece
3. Materials Science and Technology Department, University of Crete, 71003 Heraklion, Greece
4. Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia