1. Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, United States
2. Physics Department, Georgetown University, 37th and O Sts. NW, Washington, D.C. 20057, United States
3. Thermal Energy Conversion Material Research Group, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109-8099, United States