1. Contribution from the Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya, 464-8603, Japan, Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji 192-0397, Japan, Department of Chemistry, Tohoku University & CREST, Aramaki, Aoba-ku, Sendai 980-8578, Japan, and Institute of Solid State Physics, University of Tokyo, Kashiwa, 277-8581, Japan