1. Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France