H. H. Li. Refractive index of alkali halides and its wavelength and temperature derivatives. J. Phys. Chem. Ref. Data5, 329-528 (1976) and references therein. * Sellmeier formula is derived by critical analysis of experimental data from several sources.
Potassium bromide (KBr) is a salt commonly used in the form of a transparent crystal for a variety of optical applications. Its wide transmission range, extending from the ultraviolet into the far-infrared spectrum, makes it a popular choice for infrared spectroscopy. KBr is also used as a substrate material for specialized optical coatings. It is hygroscopic, meaning it readily absorbs moisture from the air, so care must be taken in its handling and storage to maintain its optical properties. It is not advisable for applications where it would be exposed to high moisture or extreme environmental conditions. Despite its hygroscopic nature, KBr is highly valued for its excellent transmission characteristics and is a staple in various optical and spectroscopic setups.