Cascade Energy Transfer in CeF₃ Crystals

The emission spectra of the CeF₃ crystals in UV-visible region and their temperature dependence in the range of 6-453 K under UV, VUV excitation as well as their excitation spectra (4-25 eV) have been studied. The 350 nm emission band from perturbed Ce³⁺ can be excited by 295.2 and 302.4 nm emissions from the regular Ce³⁺. The 350 nm emission band, in turn, can excite the emission bands centered at 470 and 535 nm caused by some defects below room temperature. These results show that there is a cascade energy transfer process from regular Ce³⁺ to quenching centers via perturbed Ce³⁺ and defect centers in the CeF₃. Meanwhile, thermoluminescence, giving peaks at about 240 and 300°C has been discovered, and the corresponding deep traps with depth ∼ 1 eV are found to be a kind of quenching center for CeF₃ luminescence at room temperature.