1. Institute for Bioengineering of Catalonia, Barcelona Institute of Science and Technology, Barcelona 08028, Spain
2. Helmholtz-Institut Mainz, GSI Helmholtzzentrum für Schwerionenforschung, Mainz 55128, Germany
3. Institute for Physics, Johannes Gutenberg-Universität Mainz, Mainz 55099, Germany
4. International Tomography Center SB RAS, Novosibirsk 630090, Russia
5. Boreskov Institute of Catalysis SB RAS, Novosibirsk 630090, Russia
6. Department of Physics, University of California, Berkeley, CA 94720-7300, USA