CdWO4:Sm single crystals were studied by optical, electron-paramagnetic and thermoluminescence spectroscopy in the temperature range of 4–750 K. A hopping diffusion of self-trapped excitons and energy transfer to Sm3+ centres is demonstrated. The mechanism of energy transfer includes the formation of a Sm3+ bound exciton either by direct excitation or in the result of a thermally stimulated hopping diffusion of self-trapped excitons as well as a sequential trapping of charge carriers near the Sm3+ ions. The energy transfer from the perturbed excitons to Sm3+ ions is controlled by an electric dipole-dipole or exchange interaction and it is terminated in the temperature range of 450–650 K due to the thermal destruction of Sm3+-perturbed excitons. In the case of near-surface excitations created in the energy region of high absorption coefficients by 5-eV photons, the Sm3+ emission is additionally quenched by surface-induced quenching centres.
- Cadmium tungstate
- Electron-paramagnetic resonance
- Energy transfer
- Exciton mobility
- Samarium impurity