1. Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauki 46, 252650 Kiev, Ukraine
2. Chair of Physics, Rzeszów University of Technology, ul. Pola 2, PL-35-959 Rzeszów, Poland
3. Institute of Physics, University of Rzeszów, ul. Rejtana 16A, PL-35-310 Rzeszów, Poland