Edvard Kokanyan 1, 2, Anush Movsesyan 1, 2, Marco Bazzan 3
1 Armenian State Pedagogical University After Kh. Abovyan, Yerevan, Armenia, 2 Institute for Physical Research, National Academy of Sciences of Armenia, Ashtarak, Armenia, 3 Physics and Astronomy Department, Universita di Padova, Padova, Italy