Ångström
The ångström (Swedish: [ˈɔŋstrøm]) or angstrom is a unit of length equal to 6990100000000000000♠10−10 m (one ten-billionth of a metre) or 6990100000000000000♠0.1 nm. Its symbol is Å, a letter in the Swedish alphabet.
The natural sciences and technology often use ångström to express sizes of atoms, molecules, microscopic biological structures, and lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation, and dimensions of integrated circuit parts. Atoms of phosphorus, sulfur, and chlorine are about an ångström in covalent radius, while a hydrogen atom is about half an ångström; see atomic radius.
The unit is named after the Swedish physicist Anders Jonas Ångström (1814–1874). The symbol is always written with a ring diacritic, as the letter in the Swedish alphabet. The unit's name is often written in English without the diacritics, but the official definitions contain diacritics.
Use
The ångström is used extensively in crystallography, solid-state physics and chemistry as a unit for d-spacings (the distance between atomic planes in a crystal), cell parameters, inter-atomic distances and x-ray wavelengths, as these values are often in the 1–10 Å range. For example, the Inorganic Crystal Structure Database presents all these values using the ångström.
