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 ðC 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.
Caesium bromide can be prepared via neutralization reactions:
It can also be prepared by direct synthesis:
The direct synthesis is a vigorous reaction of caesium with bromine. Due to its high cost, it is not used for preparation.
Caesium bromide is sometimes used in optics as a beamsplitter component in wide-band spectrophotometers.