1. Wigner Research Centre for Physics, Budapest, Hungary
2. Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, AL, USA
3. Department of Atomic Physics, Institute of Physics, Budapest University of Technology and Economics, Budapest, Hungary
4. Fachbereich Physik, Philipps-Universität Marburg, Marburg, Germany
5. Institute for Advanced Study, Technical University of Munich, Garching, Germany