Afterglow and photoconductivity in europium-doped alkali halides

Luminescence persistence (afterglow) after uv irradiation of alkali halides doped with ${\mathrm{Eu}}^{2+}$ has been investigated. The wavelength dependence of the afterglow emission and excitation, photoconductivity, and thermoluminescence were measured in different host matrices (NaCl, KCl, KBr, KI:${\mathrm{Eu}}^{2+}$). Parallel behavior of the afterglow and photoconductivity data has been found, which leads us to consider ${\mathrm{Eu}}^{2+}$ ionization as the primary process of the afterglow. Thermoluminescence measurements in the liquid-nitrogen–room-temperature range show the existence of a distribution of electron traps, which could account for the temporal dependences observed in the luminescence emission.