1. Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Kohoku-ku,
Yokohama 223-8522, Japan
2. Institute of Materials
Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801,
Japan
3. Department
of Applied
Physics, Hanyang University, ERICA 426-791, Republic of Korea
4. Ertl Center for
Electrochemistry and Catalysis, Gwangju Institute of Science and Technology, Gwangju 500-712,
Korea