1. Department of Chemistry, Memorial University, St. John's, Newfoundland, A1B 3X7, Canada, Department of Chemistry, Kent State University, Salem, Ohio 44460, Institute de Physique Electronique et Chimie Laboratoire de Physique des Milieux Denses, Paul Verlaine University, 1 Bd Arago F-57078, Metz, France, and Physikalisches Institut III, Universität Erlangen-Nürnberg, Erwin-Rommel-Strasse 1, 91058 Erlangen, Germany