Luminescence of yttrium–aluminum garnet crystals with Eu$^{2+}$ impurity ions

Luminescence of yttrium-aluminum garnet Y$_{3}$Al$_{5}$O$_{12}$ : Eu,Si samples is studied. It is found that luminescence is associated with Eu$^{2+}$ ions, but does not correspond to intracenter 4$f^{6}$5$d^{1}$–4$f^{7}$ transitions. Measurements of the excited state lifetime point to the luminescence mechanism involving charge-transfer states.