1. Department of Physical Chemistry and Biochemistry, Ludwig-Maximilians-Universität Munich, Butenandtstrasse 5-13 (E), 81377 Munich, Germany, Institute of Physical Chemistry and Electrochemistry, Gottfried Wilhelm Leibniz Universität Hannover, Callinstrasse 3-3a, 30167 Hannover, Germany, and J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 18223 Prague 8, Czech Republic