The cesium iodide crystal is often used as the scintillator material of the electromagnetic calorimeter in particle physics experiments. Cesium iodide can be used as a spectrometer in Fourier transform spectroscopy (FT-IR). Compared with the more commonly used potassium bromide spectroscope, cesium iodide has a wider range of light transmission, and the band used can be extended to far infrared. But there is a problem with Chemicalbook. The optical cesium iodide crystal is very soft and has no cleavage, so it is difficult to make a flat polished surface. In addition, the cesium iodide optical crystal must be stored in a dry container to prevent water from reacting with cesium iodide. Plating a layer of germanium on the surface of cesium iodide can minimize the impact of exposure to moisture in the air when switching the splitter.