1. Jacobs University, School of Engineering and Science, P.O. Box 750 561, 28725 Bremen, Germany
2. Laboratoire de Chimie Physique, UMR 8000 CNRS, Université Paris-Sud 11, 91405 Orsay Cedex, France
3. Department of Chemistry and Biochemistry, Florida State University and Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Tallahassee, Florida 32306−4390