The diffusion of O-- ions into CaF2:Sm2+ crystals has been directly observed by means of the decoloration of the crystals. In the presence of water vapor the O-- ions penetrate easily into the crystals, but in an O2 atmosphere penetration is quite limited. The penetration is isotropic, and the activation energy for diffusion is estimated to be 45±4 Kcal/mole. The dependence of the Sm3+ fluorescence on the penetration process has also been investigated. The emission spectrum of Sm3+ ions in the transparent zone shows the presence of both Type I(C3) and Type II(C4) centers. It was found that Sm3+ ions are charge compensated not only by O-- ions but also by interstitial - ions, in spite of thermal treatment in an H2O atmosphere. The emission spectrum in the opaque zone shows only Type I centers. © 1968.
