1. Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, Chemistry Program, Roosevelt University, Chicago, Illinois 60605, Istituto di Fisica Atomica e Molecolare, CNR, 56127 Pisa, Italy, Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, and Department of Chemistry, Northwestern University, Evanston, Illinois 60208