Photoconductivity and luminescence efficiency of rare earth activated insulating materials

In this article, we discuss the nature of the high lying states in rare earth activated systems and their effect on the luminescence efficiency of these systems. We show that by comparing the optical spectra of these materials with complementary measurements such as photoconductivity (PC), the absolute energy level structure of the ions with respect of the intrinsic bands of the host can be determined. We propose new measurements which will provide insight on the manner in which energy delocalizes in activated solids.