1. Fundamental and Environmental Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba 305-8501, Japan, SORST, Japan Science and Technology Agency, c/o NEC Corporation, 34 Miyukigaoka, Tsukuba 305-8501, Japan, Department of Chemistry, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, ERATO, Japan Science and Technology Agency, PRESTO, Japan Science and Technology Agency, Meijo University, 1-501 Shiogamaguchi, Nagoya 468-8502, Japan