1. Institute of Physics, University of Neuchâtel, Rue Emile-Argand 11, CH-2009 Neuchâtel, Switzerland, Department of Chemistry, Durham University, Durham, DH1 3LE, U.K., Swiss Norwegian Beamlines at ESRFBP-220, 38043 Grenoble, France, and Laboratoire de Crystallographie, Ecole Polytechnique Fédéral de Lausanne, CH-1015 Lausanne, Switzerland