1. Contribution from the TCM Group, Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, U.K., Department of Physics, University of Warwick, Coventry CV4 7AL, U.K., Laboratiore de Minéralogie-Cristallographie de Paris, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex, France, Química-Física Molecular, Department of Chemistry, FCTUC, University of Coimbra, 3004-535 Coimbra, Portugal, and CICECO, Department of Chemistry, University of Aveiro, 3810-193 Aveiro,...