Effect of X-rays on the valence state of europium in Y$_{2}$O$_{3}$ : Eu$^{3+}$ phosphor

The effect of X-ray radiation on the valence state of europium ions in the Y$_{2}$O$_{3}$ matrix was studied by EPR. The alternation of the charge of europium ions (Eu$^{3+}$ $\to$ Eu$^{2+}$ $\to$ Eu$^{3+}$) in the Y$_{2}$O$_{3}$ structure was detected. The mechanism of europium reduction to the divalent state under the action of X-ray irradiation is described.