1. Inorganic Chemistry and Catalysis Debye Institute for Nanomaterials ScienceUtrecht University Universiteitsweg 99 3584 CG Utrecht The Netherlands
2. Department of PhysicsUniversity of Helsinki PO Box 64 00014 Helsinki Finland
3. Dutch-Belgian Beamline BM26European Synchrotron Radiation (ESRF) Facility CS 40220 38043 Grenoble Cedex 9 France
4. Istituto per lo Studio dei Materiali Nanostrutturati (ISMN)-CNR, USO Via Ugo La Malfa, 153 90146 Palermo Italy