1. Department of Chemistry; University of Oslo; P.O. Box 1033 0315 Oslo Norway
2. ESRF-The European Synchrotron; CS40220 38043 Grenoble France
3. Department of Chemistry; University of Pavia and INSTM; Viale Taramelli 16 27100 Pavia Italy
4. College of Engineering; Swansea University; Swansea SA1 8EN UK