1. Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Laboratoire de Physique, École Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 7, France, and Department of Mathematics and Natural Sciences, College of Science Cardinal Stefan Wyszyński University, Dewajtis 5, 01-815 Warsaw, Poland