1. Institute for Solid State Physics, University of Tokyo,
Kashiwa, Chiba 277-8581, Japan
2. Department of Energy & Hydrocarbon Chemistry, Kyoto University, Kyoto 615-8510, Japan
3. National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6100, United States
4. Toyota Physical and Chemical Research Institute, Nagakute, Aichi 480-1192, Japan