1. Facultiy of Physics, Taras Shevchenko National University of Kyiv, Volodymyrska Str. 64/13, 01601 Kyiv, Ukraine
2. Facultiy of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska Str. 64/13, 01601 Kyiv, Ukraine
3. Department of Physics and Mathematics, University of Eastern Finland, Yliopistokatu 7, FI-80101 Joensuu, Finland