X-ray induced changes in the optical properties of SrF₂:Co

The optical absorption spectrum of X-irradiated SrF₂:Co is reported. It shows two bands at 290 nm and 340 nm. When the irradiation is performed at 70K, a broad band in the 300 nm region is also produced. The 290 nm and 340 nm absorption bands are associated with Co⁺ ions created by X-irradiation, and the broad band is identified as due to V_K centres. The X-ray excited emission and the emission excited by light in X-irradiated samples are reported. In both cases the emission spectrum shows four emission bands which are associated with Co²⁺ electronic transitions. The excitation spectra of all of these bands coincides with the absorption one. A model is proposed to explain the emission properties.