Studies of photoinductive dichroism allow to define the orientation of colour centres. The photoinductive dichroism of absorption testifies the fact that oscillators, responsible for the long-wave absorption band of M þ A -centres, are located along h100i crystallographic directions, and high-energetic oscillators, along h110i crystallographic directions. Various impurities cause unequal perturbations in the crystal lattice. The determination of the kinetic parameters of the reorientation processes in simple and complex colour centres allows establishing the structure of the aggregative centre. The size of the impurity ion influences the energy of reorientation of M þ A -centres, and this, in turn, is connected with the displacement of vacancies towards the anion sites of the crystal. It is found that the anion vacancy in M þ A -centres jumps in h110i directions, but in F þ A -centres it jumps in h100i directions. Z. P. Chornyi et al.: Reorientation of M þ A -Centres in CaF 2 : Me + Crystals

The spectral and kinetic parameters of electron-pulse-initiated transient absorption of oxygen-doped CaF 2 crystals were studied using pulsed spectrometry with a nanosecond time resolution. It is shown that the formation of a M + A color centers in CaF 2 -0.01M%CaO crystals occurs by thermally activated diffusion of the vacancies. Activation energy of M + A color centers formation process of 0.4 eV is established.

The spectral and kinetic parameters of electron-pulse-initiated transient absorption and luminescence of nominally pure CaF 2 crystals were studied using pulsed spectrometry with nanosecond time resolution. The effect of temperature on the formation of defects was studied. It was established that on increasing the temperature F-H pairs and unknown defects are created. Laser-induced change is studied by optical absorption and luminescence due to F-H pairs generated by an electron pulse in CaF 2 .

The parameters of radiation sensitivity of the oxygen-doped fluorite crystals were calculated in a onedimensional model. The limit concentrations of the color centers as a function of the concentration of the oxygen impurity in the fluorite crystal were defined. Fluorite crystals with anti-Frenkel defects in the anion sublattice of the crystal have a specific property: the discolored after irradiation crystal being irradiated repeatedly with ionizing radiation retains the "memory" of the preceding irradiation. Using an ion chain model this paper studies under what conditions the "radiation memory" effect can arise in the MeF2-O 2− crystals as well as the extent of its contribution into the overall radiation sensitivity of the crystal.

The paper presents the results of a study of thermo-and photostimulated transformations of colour centres in doped fluorite crystals. By means of certain sequence of such operations one can double the concentration of working MA + -colour centres.