1. Faculty of Materials Science and Technology, Slovak University of Technology, Paulínska 16, 917 24 Trnava, Slovak Republic, Laboratory of Theoretical Chemistry, Institute of Chemistry,Eötvös University, P.O. Box 32, H-1518, Budapest 112, Hungary, Institute of Advanced Simulation, Jülich Supercomputer Centre, Research Centre Jülich GmbH D-52425 Jülich, Germany, and Groupe de Spectromé trie Moléculaire et Atmosphérique, Reims University, F-51687, Reims Cedex 2, France