1. Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
2. Lehrstuhl für Biomedizinische Physik, Physik-Department, Technische Universität München, 85747 Garching, Germany
3. University of Montpellier 2, UMR 5253, ICGM, C2M, CC1504, Montpellier, France
4. Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Universita di Torino, I-10125, Torino, Italy
5. Department of Physics and Astronomy, University College London, London, United Kingdom