1. Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Prague 6 166 28, Czech Republic
2. Department of Dynamics of Molecules and Clusters, J. Heyrovský Institute of Physical Chemistry, v.v.i., The Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
3. Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K.