1. Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
2. Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
3. Department of Chemistry, Graduate School of Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan