1. Department of Chemistry, Norwegian University of Science and Technology, N-7491 Trondheim, Norway, Swiss Norwegian Beamlines, European Synchrotron Radiation Facility, F-38043 Grenoble, France, and Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale “A. Avogadro”, Via V. Bellini 25/G, 15100 Alessandria, Italy