Cathodoluminescence mechanism of crystalline Gd₂SiO₅:Ce

Complex luminescence decay kinetics have been observed in Gd₂SiO₅:Ce crystals under electron beam irradiation. Absorption and photoluminescence excitation spectra, decay kinetics in various excitation bands over a wide range of photon energies from 3.6 to 7.0 eV in the temperature region from 80 to 400 K as well as the spectra of the glow curve creation efficiency at 80 K are examined. It is shown that the free electronic excitations produced, depending on the absorbed photon energy, have different recombination mechanisms finally leading to the radiative transitions between the 5d² E configuration and the 4f configuration of the Ce³⁺ ion. At hv_exc < 6.1 eV a single exponential decay caused by direct recombination via a 5d² E configuration of the Ce³⁺ ion takes place, whereas at hv_exc ≥ 6.1 eV an additional slow exponential recombination process occurs. The latter is represented by the two-stage recombination via either the quasi-local 6s level of Ce³⁺ lying in the conduction band of the localized states arising due to the perturbation of the host lattice by an impurity Ce³⁺ ion.