1. Department of Chemistry School of Science The University of Tokyo 7‐3‐1 Hongo, Bunkyo‐ku Tokyo 113‐0033 Japan
2. Department of Materials Science Faculty of Pure and Applied Sciences University of Tsukuba 1‐1‐1 Tennodai Tsukuba Ibaraki 305–8577 Japan
3. Department of Physics School of Science The University of Tokyo 7‐3‐1 Hongo, Bunkyo‐ku Tokyo 113‐0033 Japan
4. Institute of Laser Engineering Osaka University 2‐6 Yamadaoka Suita Osaka 565–0871 Japan
5. Analysis Systems Solution Development Dept. Metrology and Analysis Systems Product Div. Hitachi High‐Tech Corporation 3‐2‐1 Sakado, Takatsu‐ku Kawasaki Kanagawa 213‐0012 Japan
6. Recording Media Research & Development Laboratories FUJIFILM Corporation 12‐1, Ohgi‐cho 2‐Chome Odawara‐shi Kanagawa 250‐0001 Japan