New ultrafast scintillators with core valence luminescence: Cs2MgCl4 and Cs3MgCl5

Abstract

Future experiments in high energy physics and medical imaging require radiation detectors having properties which are not presently available. The main limitations arise from a lack of suitable scintillation crystals. This dilemma prompts the need for research leading to the discovery of new fast and bright scintillator materials that combine unique properties to fulfil modern experiment requirements without compromises. In this work, single crystals of Cs₂MgCl₄ and Cs₃MgCl₅ up to 12 mm in diameter are grown via the vertical Bridgman method. Scintillation properties are reported for the first time, and core valence luminescence is observed for both compounds. X-ray excited radioluminescence emission of Cs₂MgCl₄ is centered at 295 nm, with a scintillation decay time of 2.25 ± 0.05 ns and relatively high core-valence light yield of 2200 ± 110 ph per MeV. Cs₃MgCl₅ has two main emission peaks centered at 242 nm and 302 nm, a decay time of 1.46 ± 0.05 ns, and a light yield of 1340 ± 70 ph per MeV. The better coincidence time resolution (CTR) is obtained with Cs₂MgCl₄, which is measured to be 129 ± 4 ps FWHM. Density functional theory (DFT) calculations are also performed and provide supporting evidence that the observed scintillation originates from core valence luminescence. The combination of speed and brightness of these new scintillators could be useful for fast timing applications in which moderately dense materials are required.