into visible light that are further captured and converted into electrical signals by a following photomultiplier. [7][8][9][10][11] Scintillators have been actively utilized for radiation detection applications in many fields, like nondestructive inspection, medical imaging, and space exploration. Scintillator-based X-ray detectors are advantageous in terms of cost and stability than direct X-ray detectors (a-Se), and the current market of X-ray detectors is dominated by scintillators.The light yield of scintillators, as one of the most important figures of merit, determines the X-ray conversion efficiency and detection contrast. Liu and co-workers reported the good X-ray imaging properties from CsPbBr 3 nanocrystals [8] and Zhang et al. evaluated the light yield for CsPbBr 3 nanocrystals as 21 000 photons per MeV. [11] Such value is still much lower than traditional scintillators like Lu 1.8 Y 0.2 SiO 5 -Ce (LYSO, 33 200 photons per MeV), [12] CsI-Tl (54 000 photons per MeV) [12] and Gd 2 O 2 S-Tb (GOS, 60 000 photons per MeV) [13] etc. The major reason is that the small Stokes shift and the self-absorption effect for lead halide perovskites would severely restrict the light outcoupling efficiency in films and crystals, which require large thickness for complete X-ray attenuations. For scintillators, large Stokes shift and high photoluminescence efficiency are required to obtain high scintillation light yield. The recently emerged self-trapped exciton emissions from low dimensional perovskites exhibit large stokes shift and high PLQY, and may provide efficient X-ray scintillations, but have scarcely been studied. [14][15][16] Another severe issue restricting the applications of lead halide perovskite scintillators is the toxicity of lead element. The ionic nature of halide perovskites and high solubility in water may seriously harm the human health as well as the environment. It is thus of great significance to find lead-free perovskites or halide scintillators.Here we present 1D structured Rb 2 CuBr 3 as one new member of scintillators with exceptionally high light yield. Rb 2 CuBr 3 is obtained by direct reaction between RbBr and CuBr with phase-purity, high quality, and good stability. Its 1D crystal structure and soft crystal lattice facilitate the formation of self-trapped exciton, which emits at 385 nm with a large Stokes shift of 85 nm (0.91 eV) and 98.6% photoluminescence quantum yield. The high emission efficiency, large Stokes shift, strong X-ray attenuation, and good spectrum matching with the photomultiplier tube (PMT) or silicon photomultiplier Scintillators are widely utilized for radiation detections in many fields, such as nondestructive inspection, medical imaging, and space exploration. Lead halide perovskite scintillators have recently received extensive research attention owing to their tunable emission wavelength, low detection limit, and ease of fabrication. However, the low light yields toward X-ray irradiation and the lead toxicity of these perovskites severely restricts their practical ...

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We demonstrate the possibility in quantifying the Raman intensities for both specimen and substrate layers in a common stacked experimental configuration and, consequently, propose a general and rapid thickness identification technique for atomic-scale layers on dielectric substrates. Unprecedentedly wide-range Raman data for atomically flat MoS(2) flakes are collected to compare with theoretical models. We reveal that all intensity features can be accurately captured when including optical interference effect. Surprisingly, we find that even freely suspended chalcogenide few-layer flakes have a stronger Raman response than that from the bulk phase. Importantly, despite the oscillating intensity of specimen spectrum versus thickness, the substrate weighted spectral intensity becomes monotonic. Combined with its sensitivity to specimen thickness, we suggest this quantity can be used to rapidly determine the accurate thickness for atomic layers.