1. Department of Material Development, Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, 1233 Watanuki-machi, Takasaki 370-12, Japan, Gesellschaft für Schwerionenforschung mbH, Plankstrasse 1, D-64291 Darmstadt, Germany, and Department of Chemistry, Gunma University, Tenjin-cho, Kiryu 376, Japan