1. Department
of Physics, Budapest University of Technology and Economics, H-1521 Budapest, Hungary
2. Department
of Physical Chemistry, Babes-Bolyai University, RO-400028 Cluj-Napoca, Romania
3. Penn
State Berks College, The Pennsylvania State University, Reading, Pennsylvania 19610, United States
4. Faculty
of Applied Sciences, Université Libre de Bruxelles, CP165/63,
Av. F. Roosevelt 50, 1050 Brussels, Belgium