1. Department of Nuclear Chemistry, Chalmers University of Technology, Fack, S-402 20 Göteborg 5, Sweden.
2. Institut für Kernchemie, Johannes Gutenberg Universität, Postfach 3980, D-6500 Mainz, Germany.
3. Department of Nuclear Chemistry, University of Oslo, Oslo 3, Norway.
4. Department of Nuclear Chemistry, University of Oslo, Oslo 3, Norway