Thermally stimulated depolarization of Eu2+-cation vacancy dipoles in alkali halide single crystals

Ionic thermocurrent (ITC) measurements have been performed on eight alkali halide single crystals doped with divalent europium. In all cases, the observed ITC peaks were fitted with a mono-energetic model without to appeal to any dipole-dipole interaction. Values for the reorientation parameters have been calculated. The relationship T_M1nτ^?1 α E previously found for I–V complexes in alkali halides has been found to be very well obeyed for the experimental data obtained in this investigation. It is also reported that the logarithm of the experimentally determined energies for free dipole reorientation shows a linear dependence on the interaction distance between the Eu²⁺ ion and the surrounding halogen ions in the distorted cubic site occupied by this impurity in the alkali halides.