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.