Caesium iodide

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Caesium iodide
Caesium iodide
IUPAC name
Caesium iodide
Other names
Cesium iodide
3D model (Jmol)
ECHA InfoCard 100.029.223
EC Number 232-145-2
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 1,277 °C (2,331 °F; 1,550 K)
440 g/L (0 °C)
-82.6·10−6 cm3/mol
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
Francium iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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]

Monatomic caesium halide wires grown inside double-wall carbon nanotubes.[3]

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 is used as a beamsplitter in Fourier transform infrared (FTIR) spectrometers. It has a wider transmission range than the more common potassium bromide beamsplitters, extending its working range into the far infrared. However, optical-quality CsI crystals are very soft and a hard to cleave or polish. They should also be coated (typically with germanium) and stored in a desiccator, to minimize interaction with atmospheric water vapors.[4]

Caesium iodide atomic chains can be grown inside double-wall carbon nanotubes. Accurate measurements reveal that in such chains I atoms appear brighter than Cs atoms despite having a smaller mass. This difference was explained by the charge difference between Cs atoms (positive), inner nanotube walls (negative) and I atoms (negative). As a result, Cs atoms are attracted to the walls and vibrate more strongly than I atoms, which are pushed toward the nanotube axis.[3]


  1. ^ a b Cesium iodide. U.S. National Library of Medicine
  2. ^ Kowalski, M. P.; Fritz, G. G.; Cruddace, R. G.; Unzicker, A. E.; Swanson, N. (1986). "Quantum efficiency of cesium iodide photocathodes at soft x-ray and extreme ultraviolet wavelengths". Applied Optics. 25 (14): 2440. doi:10.1364/AO.25.002440. PMID 18231513. 
  3. ^ a b Senga, Ryosuke; Komsa, Hannu-Pekka; Liu, Zheng; Hirose-Takai, Kaori; Krasheninnikov, Arkady V.; Suenaga, Kazu (2014). "Atomic structure and dynamic behaviour of truly one-dimensional ionic chains inside carbon nanotubes". Nature Materials. 13 (11): 1050. doi:10.1038/nmat4069. PMID 25218060. 
  4. ^ Sun, Da-Wen (2009). Infrared Spectroscopy for Food Quality Analysis and Control. Academic Press. pp. 158–. ISBN 978-0-08-092087-0.