1. Department of Chemistry and Laboratory of Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012, Department of Chemistry and Biochemistry and Center for Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306-4390, and Intense Pulsed Neutron Source, Argonne National Laboratory, Argonne, Illinois 60439