1. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
2. Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
3. ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Chilton Didcot OX11 0QX, U.K.
4. Institut Laue-Langevin, 71 avenue des Martyrs, 38000 Grenoble, France