1. Faculty of Sciences, Department of Physical Chemistry, University of P. J. Šafárik in Košice, Moyzesova 11, 04154 Košice, Slovakia
2. Westfälische Wilhelms-Universität Münster, Physikalisches Institut, Münster, Germany
3. Faculty of Science, Department of Physical Chemistry, Comenius University, Mlynská Dolina II, Bratislava, Slovakia
4. SIX Center, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technická 3058/10, 31600 Brno, Czech Republic
5. Institute of Physics, Faculty of Sciences, University of P. J. Šafárik in Košice, Park Angelinum, 04154 Košice, Slovakia