Photoluminescence of Dy3+ and Dy2+ in NaMgF3:Dy: A potential infrared radiophotoluminescence dosimeter

Abstract Infrared-emitting radiophotoluminescence centres were observed in NaMgF3:Dy in the form of stable Dy2+ ions that formed only after exposure to ionising radiation. Prior to irradiation, only Dy3+ luminescence could be seen. During radiation exposure, energetic electrons were captured by Dy3+ to form Dy2+, and the Dy2+ electron trap was approximately 3 eV deep and stable at room temperature. The large trap depth allowed for non-destructive probing of the Dy2+ photoluminescence via excitation into the lowest energy 5d state at 640 nm. Exciting into higher energy states at 340 nm resulted in ionisation of the trapped electrons, restoring the radiation-induced Dy2+ to Dy3+, and demonstrated that the material can be optically reset. The intraconfigurational 4f10 transitions of Dy2+ were compared with those of the isoelectronic Ho3+ ion in similar host compounds and attributed to specific transitions in all cases. The infrared radiophotoluminescence can potentially be used for real-time fibre optic dosimetry, as the Cherenkov component is significantly lower in the infrared when compared to emissions in the visible region.