1. Laboratory of Physical Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 Helsinki, Finland
2. Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
3. Department of Physical Sciences, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland