Deciphering the Mechanism of Ultrafast Scintillation in 1D Silver Halides

The development of ultrafast scintillators is critical to the GHz X-ray and time-of-flight (TOF) imaging techniques. Low-dimensional silver-based halides have emerged as promising candidates due to high radioluminescence efficiency and ultrafast decay time. However, the ultrafast scintillation mechanism in silver-based halides, such as Rb₂AgBr₃ (RAB), remains controversial. Here, the study reveals the origin of ultrafast scintillation timing response in melt-grown RAB bulk crystals. The RAB shows light-yellow emission with a photoluminescence quantum yield (PLQY) of 13.9%. Under the picosecond (ps) pulse X-ray irradiation, RAB has an ultrafast decay time of 3.2 ns that accounts for 40.5% of the total emitted light. The light yield is estimated as 3100 photons MeV⁻¹ under ²²Na irradiation. Based on the temperature-dependent radioluminescence (RL) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and spectrally resolved thermally-stimulated luminescence (TSL) glow curves, it is confirmed that the bromine vacancy as the F-center is the origin of the ultrafast scintillation component. These findings provide elaborated and fundamental insights into the ultrafast luminescent mechanisms of low-dimensional silver-based halides, thereby opening up new design horizons in the development of ultrafast scintillators.