1. Institut Laue-Langevin, 71 avenue
des Martyrs, CS 20156, 38042 Grenoble, Cedex 9, France
2. Research
School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
3. Department
of Chemistry, University of Reading, P.O. Box 224, Reading RG6 6AD, U.K.
4. Institute
of Chemistry, Eötvös Loránd University, Budapest 112,
P.O. Box 32, H-1518 Hungary