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The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]

Fast scintillation materials based on ternary halide mixed crystals, Cs(Ca 1−x Mg x)Cl 3 , were synthesized. The luminescence at the defects or impurity sites within the band-gap excitation were observed. Upon X-ray excitation, bands corresponding to the intrinsic Auger-free luminescence (AFL) for CsCaCl 3 and CsMgCl 3 were observed, and the wavelength of the mixed crystals bands was similar to that of CsCaCl 3. Cs(Ca 1−x Mg x)Cl 3 exhibited a short decay time, which is typical for AFL in CsCl-based compounds, and CsMgCl 3 exhibited the shortest decay time of 1.1 ns and the smallest proportion of the first component (65%). On the other hand, CsCaCl 3 exhibited the longest decay time constant of 2.0 ns and the largest proportion of the first component (92%). The light yields of the fast components for CsCaCl 3 were larger than that of BaF 2 , whereas the light yields of the mixed crystals were lower than those of CsCaCl 3 and CsMgCl 3. The proportion of Cs/Mg in the mixed crystals was expected to affect the decay time constants and light yields, but changes in these properties did not vary much with Cs/Mg ratio. • Auger-free luminescence band was clearly observed under X-ray excitation for Cs(Ca 1−x Mg x)Cl 3. • Cs(Ca 1−x Mg x)Cl 3 exhibited short scintillation decay time constants of less than 2.0 ns. • The fast component light yields of CsCaCl 3 was larger than that of BaF 2 [ABSTRACT FROM AUTHOR]