Caesium iodide

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Caesium iodide
Image:Caesium iodide.jpg
General
Systematic name	Caesium iodide
Molecular formula	CsI
Molar mass	259.8 g/mol
Appearance	?
CAS number	[7789-17-5] [1]
Properties
Density and phase	4.51 g/cm3, solid
Solubility in water	44 g/100 ml (0 °C)
Melting point	621 °C
Boiling point	1277±5 °C

Caesium iodide (CsI) is an ionic compound often used as the input phosphor of an x-ray image intensifier tubes found in fluoroscopy equipment.

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 usefulness in to the far infrared. A problem with optical-quality CsI crystals are they are very soft with no clevage, 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.

[edit] Optical properties

• Transmission range: 250 nm to 55 µm
• Refractive index: 1.739 at 10.6 µm
• Reflection loss: 13.6% @ 10.6 µm (2 surfaces)

[edit] Physical properties

• Hardness (Knoop): 137.9 kPa (20 lbf/in²)
• Young's modulus: 5.3 GPa (769 lbf/in²)
• Modulus of rupture: 5.6 GPa (810 lbf/in²)
• Apparent elastic limit: 5.6 GPa (810 lbf/in²)
• Structure: Cubic, no cleavage

[edit] External links

• Links to external chemical sources.