1. Department of Chemistry and Biotechnology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan
2. Department of Specialty Materials, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263, Japan
3. Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, 1233 Watanuki-machi, Takasaki, Gunma 370-12, Japan