Investigation of cross luminescence in lanthanum fluoride as a potential fast-response scintillator

We report the potential of lanthanum fluoride (LaF₃) as a fast-response scintillator. When excited by an extreme ultraviolet free electron laser, neodymium-doped LaF₃ (Nd³⁺:LaF₃) exhibited a 1.9 ns fast decay component and a 6.7 ns slow decay component for its 172 nm emission peak. The slow decay component is due to interconfigurational 4f²5d-4f³ transition in Nd³⁺. First principles density functional theory calculations using the Perdew-Burke-Ernzerhof hybrid functional including exact exchange (PBE0) and the Green's function and screened Coulomb interaction (GW) approximation as implemented in the Vienna Ab initio Simulation Package using plane-wave basis sets within the projector-augmented wave method elucidate the electronic structure of LaF₃ and reveal that the fast decay component could be due to partial cross luminescence (CL) from the bottom of the valence band to the top of the outermost core band. The presence of CL alludes to the potential of LaF₃ as a fast-response scintillator.