1. Department
of Chemistry, University of California at Berkeley, Berkeley, California 94720-3220, United States
2. Department
of Physics, University of California at Berkeley, Berkeley, California 94720-7300, United States
3. Magnetic
Resonance Research Centre, Department of Chemical Engineering and
Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, U.K.
4. Materials
Science Division, Lawrence Berkeley National Laboratory, Berkeley California 94720-3220, United States
5. Helmholtz
Institute Mainz, Johannes Gutenberg University, 55099 Mainz, Germany