Caesium bromide

Caesium bromide or cesium bromide is an ionic compound of caesium and bromine with the chemical formula CsBr. It is a white or transparent solid with melting point at 636 °C that readily dissolves in water. Its bulk crystals have the cubic CsCl structure, but the structure changes to the rocksalt type in nanometer-thin film grown on mica, LiF, KBr or NaCl substrates.

Synthesis
Caesium bromide can be prepared via following reactions:
 * Neutralization:
 * CsOH (aq) + HBr (aq) → CsBr (aq) + H2O (l)
 * Cs2(CO3) (aq) + 2 HBr (aq) → 2 CsBr (aq) + H2O (l) + CO2 (g)


 * Direct synthesis:
 * 2 Cs (s) + Br2 (g) → 2 CsBr (s)

The direct synthesis is a vigorous reaction of caesium with bromine. Due to its high cost, it is not used for preparation.

Uses
Caesium bromide is sometimes used in optics as a beamsplitter component in wide-band spectrophotometers.