1. Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
2. Department of Chemistry, Durham University, South Road, DH1 3LE, United Kingdom
3. Department of Physical Chemistry, Lund University, P.O. Box 124, S-221 00 Lund, Sweden
4. Institute of Chemistry, Eötvös Loránd University, Budapest 112, P.O. Box 32, H-1518 Hungary