1. Contribution from the Chemistry Department and Chemical Sciences Division of Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, Laboratoire de Physique Quantique, UMR 5626-CNRS, IRSAMC, Université Paul Sabatier, 118 Route de Narbonne, 31064 Toulouse Cedex 04, France, and LSDSMS, (UMR 5636-CNRS), Institut Gerhardt, cc14, Université Montpellier 2, 34095 Montpellier Cedex 5, France