1. Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
2. Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér
4, H-1111 Budapest, Hungary
3. Institute of Solid State Physics and Optics,
Wigner Research Center for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary