B.K. Ostafiychuk
Faculty of Physics and Technology, Vasyl Stefanyk Precarpathian National University, Ivano-Frankivs`k, Ukraine
I.M. Budzulyak
Faculty of Physics and Technology, Vasyl Stefanyk Precarpathian National University, Ivano-Frankivs`k, Ukraine
B.I. Rachiy
Faculty of Physics and Technology, Vasyl Stefanyk Precarpathian National University, Ivano-Frankivs`k, Ukraine
M.M. Kuzyshyn
Faculty of Physics and Technology, Vasyl Stefanyk Precarpathian National University, Ivano-Frankivs`k, Ukraine
L.O. Shyyko
Faculty of Physics and Technology, Vasyl Stefanyk Precarpathian National University, Ivano-Frankivs`k, Ukraine