1. Department of Applied Physics, Fukui University, 3-9-1, Fukui 910
2. Department of Physics, Science University of Tokyo, 1-3 Kagurazaka, Tokyo 162
3. Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Tokyo 106
4. Institute for Chemical Research, Kyoto University, Uji, Kyoto 611