Caesium iodide
CsI crystal
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Scintillating CsI crystal
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Crystal structure
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| Names | |
|---|---|
| IUPAC name
Caesium iodide
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| Other names
Cesium iodide
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.029.223 |
| EC Number |
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CompTox Dashboard (EPA)
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| Properties | |
| CsI | |
| Molar mass | 259.809 g/mol[2] |
| Appearance | white crystalline solid |
| Density | 4.51 g/cm3[2] |
| Melting point | 632 °C (1,170 °F; 905 K)[2] |
| Boiling point | 1,280 °C (2,340 °F; 1,550 K)[2] |
| 848 g/L (25 °C)[2] | |
| -82.6·10−6 cm3/mol[3] | |
Refractive index (nD)
|
1.9790 (0.3 µm) 1.7873 (0.59 µm) 1.7694 (0.75 µm) 1.7576 (1 µm) 1.7428 (5 µm) 1.7280 (20 µm)[4] |
| Structure | |
| CsCl, cP2 | |
| Pm3m, No. 221[5] | |
a = 0.4503 nm
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Lattice volume (V)
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0.0913 nm nm3 |
Formula units (Z)
|
1 |
| Cubic (Cs+) Cubic (I−) | |
| Thermochemistry | |
Heat capacity (C)
|
52.8 J/mol·K[6] |
Std molar
entropy (S⦵298) |
123.1 J/mol·K[6] |
Std enthalpy of
formation (ΔfH⦵298) |
−346.6 kJ/mol[6] |
Gibbs free energy (ΔfG⦵)
|
-340.6 kJ/mol[6] |
| Hazards | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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2386 mg/kg (oral, rat)[1] |
| Related compounds | |
Other anions
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Caesium fluoride Caesium chloride Caesium bromide Caesium astatide |
Other cations
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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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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.[7]
Synthesis and structure
Bulk caesium iodide crystals have the cubic CsCl crystal structure, but the structure type of nanometer-thin CsI films depends on the substrate material – it is CsCl for mica and NaCl for LiF, NaBr and NaCl substrates.[9]
Caesium iodide atomic chains can be grown inside double-wall carbon nanotubes. In such chains I atoms appear brighter than Cs atoms in electron micrographs 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.[8]
Properties
| Т (°C) | 0 | 10 | 20 | 25 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| S (wt%) | 30.9 | 37.2 | 43.2 | 45.9 | 48.6 | 53.3 | 57.3 | 60.7 | 63.6 | 65.9 | 67.7 | 69.2 |
Applications
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 low light yield that increases significantly with cooling.[11] 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.[12]
References
- ^ a b Cesium iodide. U.S. National Library of Medicine
- ^ a b c d e Haynes, p. 4.57
- ^ Haynes, p. 4.132
- ^ Haynes, p. 10.240
- ^ Huang, Tzuen-Luh; Ruoff, Arthur L. (1984). "Equation of state and high-pressure phase transition of CsI". Physical Review B. 29 (2): 1112. doi:10.1103/PhysRevB.29.1112.
- ^ a b c d Haynes, p. 5.10
- ^ 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.
- ^ 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.
- ^ Schulz, L. G. (1951). "Polymorphism of cesium and thallium halides". Acta Crystallographica. 4 (6): 487. doi:10.1107/S0365110X51001641.
- ^ Haynes, p. 5.191
- ^ Mikhailik, V.; Kapustyanyk, V.; Tsybulskyi, V.; Rudyk, V.; Kraus, H. (2015). "Luminescence and scintillation properties of CsI: A potential cryogenic scintillator". Phys.Stat.Sol.B. 252 (4): 804–810. doi:10.1002/pssb.201451464.
- ^ Sun, Da-Wen (2009). Infrared Spectroscopy for Food Quality Analysis and Control. Academic Press. pp. 158–. ISBN 978-0-08-092087-0.
Cited sources
- Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. ISBN 1-4398-5511-0.