EN
The optical properties of the semiconducting compounds Zn_{1-x}Co_{x}Se crystallizing in the zinc-blende structure have been investigated. The reflectivity spectra of these materials for different concentration of Co ions, have been taken out in a wide energy range between 4 and 25 eV at room (RT) and liquid nitrogen temperature (LNT) using synchrotron radiation from ADONE Storage Ring in Frascati. The comparisons between the reflectivity spectra of ternary systems and host crystal ZnSe are made. On the basis of the experimental and theoretical results, the changes of the structures of the reflectivity spectra of host crystal ZnSe caused by the influence of transition metal ions are discussed.