1. Department of Chemistry, University of Connecticut, U-3060, 55 North Eagleville Road, Storrs, Connecticut 06269-3060, Department of Physics, University of Connecticut, U-3046, 2152 Hillside Road, Storrs, Connecticut 06269-3046, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, University Avenue, Glasgow, G12 8QQ, U.K.