On the luminescence of YF3-Pr3+ under vacuum ultraviolet and X-ray excitation

The luminescence characteristic of YF3-Pr3+ under vacuum ultraviolet and X-ray excitation are identical unlike that of LaF3-Pr3+. We postulate that under X-ray excitation the energy of the electron hole recombination (exciton) in YF3 is resonant with the Pr3+ 1S0 state, while in LaF3 the exciton efficiently populates the Pr3+ 3P0 state.