About the optical properties of the Eu-ion as an impurity in non-metallic crystals

Optical data for the Eu2+ ion in different insulators and semiconductor crystals are presented. Although it is not an exhaustive review of the absorption and emission spectra observed for this ion in nonmetallic crystals, it contains the more important data that, in our opinion, have contributed to get a better understanding of the optical properties of this ion in solids. In particular, emphasis is placed on the optical data obtained by our group in the europium-doped alkali halides for which we found, for the first time, that both the absorption and emission spectra are quite sensitive to the precipitation state of the Eu2+ ions in the matrix. (author)