[7] 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.

[8] 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] and a fairly small Molière radius is 3.5 cm.

They should also be coated (typically with germanium) and stored in a desiccator, to minimize interaction with atmospheric water vapors.

[12] In addition to image intensifier input phosphors, caesium iodide is often also used in medicine as the scintillating material in flat panel x-ray detectors.