1. Consejo Superior de Investigaciones Científicas, Instituto de Ciencia de Materiales de Barcelona, (CSIC-ICMAB); Campus UAB 08193 Bellaterra Spain
2. National Institute for Lasers, Plasma and Radiation Physics; P. O. Box MG 36 Bucharest 77125 Romania
3. National Institute for Materials Physics; P. O. Box MG. 7 Bucharest 77125 Romania
4. Transilvania University of Brasov; Eroilor 29 Brasov 500036 Romania