Fig. 4: X-ray-excited multiexcitonic emissions

a RL spectra of Cs₂NaScCl₆:Sb³⁺ (0.75%) crystal under X-ray irradiation (voltage: 50 kV, dose rate: 4.5 mGy·s⁻¹), along with PersL spectra after the cessation of X-ray for 5–60 min. Insets show the RL photographs of bare and Sb³⁺-doped crystals. b PersL decay profile and photographs of Cs₂NaScCl₆:Sb³⁺ crystal after X-ray charging for 15 min. Note that the PersL decay profile was recorded after a short delay of 10 min. Inset shows the initial PersL intensity recorded immediately after the cessation of X-ray irradiation as a function of charging time. c Repeated PersL decay profile and d TL spectra of Cs₂NaScCl₆:Sb³⁺ crystal after X-ray charging. e EPR spectra of as-prepared Cs₂NaScCl₆:Sb³⁺ crystal recorded at RT. The sample was measured before and after X-ray irradiation. Note that g-factor accounts for the coupling between orbital and spin angular momentum. The g value was around 2.011 for the crystal, which possibly originated from native defects formed during synthesis⁴⁸. f Proposed mechanism of possible X-ray-activated RL and PersL process. Note that the trap states are bound with Sb³⁺ due to the absence of PersL in the host crystal, and yellow emission is extremely weak under high-energy excitation due to the relatively low energy of the STE state