Ultrafast core-to-core luminescence in BaF - LaF single crystals.

This study investigates the mechanisms underlying the ultrafast cross-luminescence observed in BaF crystals doped with LaF. 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 Ba and holes in the 5p core band of La. Ab initio calculations supported this hypothesis, showing that the energy levels of the core bands facilitate such transitions. The findings indicated that BaF-LaF scintillators hold significant promise for the detection of ultrafast processes in high-energy physics and medical applications.