1. Catalysis Research Center, Hokkaido University, Sapporo 001-0021, Japan
2. Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan
3. Surface and Interface Science Lab, RIKEN, Wako 351-0198, Japan
4. Department of Chemical Engineering, Box 351750, University of Washington, Seattle, Washington 98195-1750, United States
5. School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, United States
6. Department of Physics, Gakushuin University, Tokyo 171-8588, Japan
7. Faculty of Physical Sciences, VR-III, University of Iceland, 107 Reykjavík, Iceland