Spectral-kinetic properties of the x-ray luminescence of europium in fluorite

This paper studies the luminescence of CaF/sub 2/-Eu excited by short (10 nsec) irradiation with x-rays in order to determine the energy transfer in the crystals from the base substance to the activator. Samples were used which had been grown with a technique reducing the concentration of impurity oxygen in the crystals. The concentration of the Eu/sub 2//sup +/ ions in the crystal was determined from the absorption coefficient at the 338-nm wavelength and monitored by electron paramagnetic resonance. It is shown that the mechanism of the excitation of Eu in CaF/sub 2/ depends significantly upon the state of the activator crystal. In order to obtain the highest light yield and specific kinetic characteristics of a CaF/sub 2/-Eu crystal phosphor, one must correctly select not only a certain impurity concentration but also the optimal ratio of divalent and trivalent europium ions in the crystal.