Charge Transfer and F-Type Centers in Alkaline-Earth Fluorides Activated by Cd2+ or Zn2+ Ions

Abstract

Photoluminescence spectra of impurity centers containing anion vacancy Cd+ $${{{v}}_{a}}$$ or Zn+ $${{{v}}_{a}}$$ in alkali-earth fluorides have been studied. A comparison with luminescence spectra of photochromic centers (PCs), which can be considered as perturbed F centers, shows that luminescence of centers Cd+ $${{{v}}_{a}}$$ or Zn+ $${{{v}}_{a}}$$ is similar to that of F centers; therefore, it is caused by charge transfer from an impurity ion to an anion vacancy.