Caesium iodide


A = 4.5679 Å

Cs, I

Cesium iodide

Colorless and odorless solid


4.51 g · cm -3

626 ° C

1280 ° C.

Well in water (440 g · l-1 at 20 ° C)



2386 mg · kg -1 ( LD50, rat, oral)

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Cesium iodide (including cesium iodide ) is a white crystalline salt, with molecular formula of CsI, which is used in the IR, UV and X-ray spectroscopy. It is a salt of hydriodic acid. The material is very soft, difficult to polish and sensitive to humidity. The maximum operating temperature is 200 ° C.


Cesium iodide has a refractive index of 1.73916, and a reflection loss of 13.6 % at a wavelength of 10.0 microns. It is transparent in the range from 0.24 to 70 microns. The thermal conductivity is 1.13 W / ( m · K) and the specific heat capacity of 201 J / ( kg · K).

Cesium iodide is heat stable up to about 600 ° C, the thermal decomposition, at 670-800 ° C a.

The standard enthalpy of formation of cesium iodide is ΔHf0 = -347 kJ / mol.


Cesium iodide can be used as the transparent scintillation in scintillation counters. The high-energy radiation produces a so-called electromagnetic showers, whose photons are then transformed with a photomultiplier into a measurable electrical signal in the crystal. May undoped or thallium (Tl) or sodium (Na) as a scintillation material doped can be used.

Undoped material as it is also called in the infrared spectroscopy is used as a beam splitter.