1. Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD,
U.K.
2. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon
OX11 0QX, U.K.
3. PPSM, CNRS
UMR 8531, Ecole Normale Supérieure de Cachan, 61, avenue
du President Wilson, 94235 Cachan, France