Ultrafast core-to-core luminescence in BaF₂ - LaF₃ single crystals

This study investigates the mechanisms underlying the ultrafast cross-luminescence observed in BaF₂ crystals doped with LaF₃. We identified an ultrafast luminescent component with a decay time of approximately 150 ps, which emerges under excitation energies exceeding 24 eV as a novel radiative recombination process between electrons in the 5p core band of Ba²⁺ and holes in the 5p core band of La³⁺. Ab initio calculations supported this hypothesis, showing that the energy levels of the core bands facilitate such transitions. The findings indicated that BaF₂-LaF₃ scintillators hold significant promise for the detection of ultrafast processes in high-energy physics and medical applications.