1. J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 18223 Prague 8, Czech Republic
2. Faculty of Mathematics and Physics, Charles University, 121 16 Prague, Czech Republic
3. Institute of Physics, Lodz University of Technology, ul. Wolczanska 219, 90-924 Lodz, Poland
4. Faculty of Chemistry, University of Warsaw, ul. L. Pasteura 1, 02-093 Warsaw, Poland