1. Department of Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
2. European Synchrotron Radiation Facility, BP 220, 6 rue Horowitz, F-38043 Grenoble, France
3. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K.