Caesium iodide

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Cesium iodide
Caesium iodide
IUPAC name
Caesium iodide
Other names
Cesium iodide
7789-17-5 YesY[1]
ChemSpider 23003 YesY
EC number 232-145-2
Jmol-3D images Image
Molar mass 259.81 g/mol
Appearance white crystalline solid
Density 4.51 g/cm3, solid
Melting point 621 °C (1,150 °F; 894 K)
Boiling point 1277±5 °C
44 g/100 ml (0 °C)
Pm3m, No. 221
a = 456.67 pm
Cubic (Cs+)
Cubic (I)
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
2386 mg/kg (oral, rat)[1]
Related compounds
Other anions
Caesium fluoride
Caesium chloride
Caesium bromide
Caesium astatide
Other cations
Lithium iodide
Sodium iodide
Potassium iodide
Rubidium iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 YesY verify (what isYesY/N?)
Infobox references

Caesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an x-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly efficient at extreme ultraviolet wavelengths.[2]

An important application of caesium iodide crystals, which are scintillators, is electromagnetic calorimetry in experimental particle physics. Pure CsI is a fast and dense scintillating material with relatively high light yield. It shows two main emission components: one in the near ultraviolet region at the wavelength of 310 nm and one at 460 nm. The drawbacks of CsI are a high temperature gradient and a slight hygroscopicity.

Caesium iodide can be used in Fourier Transform Infrared (FT-IR) spectrometers as a beamsplitter. CsI has a wider transmission range than the more common potassium bromide beamsplitters, extending its usefulness into the far infrared. A problem with optical-quality CsI crystals is that they are very soft with no cleavage, making it difficult to create a flat polished surface. Also, the CsI optical crystals must be stored in a desiccator to prevent water damage to the surfaces, and coated (typically with germanium) to minimise water damage from short term atmospheric exposure during beamsplitter swapouts.

Optical properties[edit]

Physical properties[edit]


  1. ^ a b
  2. ^ M. P. Kowalski,G. G. Fritz, R. G. Cruddace, and A. E. Unzicker, and N. Swanson, Quantum efficiency of cesium iodide photocathodes at soft x-ray and extreme ultraviolet wavelengths, Applied Optics, retrieved July 2012