Affiliation: | a Institute for Chemical Reaction Science, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980, Japan b Institute of Advanced Material Study, Kyushu University, 6-1, Kasugakoen, Kasuga 816, Japan c Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980, Japan |