1. Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway
2. Institut Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, F-21078 Dijon Cedex, France
3. Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France