1. Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, and Department of Materials Science, Pennsylvania State University, University Park, Pennsylvania 16802
2. Department of Chemistry and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242
3. National Research Council, Steacie Institute for Molecular Sciences, Neutron Program for Material Research, Chalk River Laboratories, Chalk River, Ontario, Canada