1. Department
of General and Physical Chemistry, University of Pécs, Ifjúság
6, Pécs, H-7624, Hungary
2. János Szentágothai Research Center, Ifjúság 20, Pécs H-7624, Hungary
3. Department
of Physics, Beijing Normal University, 100875 Beijing, People’s Republic of China
4. Department
of Physics, Xiamen University, 361005 Xiamen, People’s Republic of China