Ultrafast core-to-core luminescence in BaF$_2$-LaF$_3$ single crystals

TL;DR

This paper uncovers a novel ultrafast core-to-core luminescence mechanism in BaF2-LaF3 crystals, with potential applications in high-speed imaging, supported by experimental observations and ab initio calculations.

Contribution

It reveals a new radiative recombination process involving core bands in BaF2-LaF3, supported by experimental data and theoretical calculations.

Findings

Ultrafast luminescence with ~150 ps decay time observed.

Luminescence occurs under excitation energies >24 eV.

Supports potential use in time-of-flight tomography.

Abstract

This study investigates the mechanisms underlying ultrafast cross-luminescence observed in BaF$_2$ crystals doped with LaF$_3$. 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 La$^{3+}$. Ab initio calculations support this hypothesis, showing that the energy levels of the core bands facilitate such transitions. The findings indicate that BaF$_2$-LaF$_3$ scintillators hold significant promise for applications in time-of-flight tomography.