angströms

Angström, symbol Å, is a unit of length equal to 10^-10 meters. It is commonly used to express atomic- and molecular-scale distances in physics, chemistry, crystallography, spectroscopy, and biology. The name honors the Swedish physicist Anders Jonas Ångström (1814–1874). The angström is not an official SI unit, but it remains widely employed in scientific literature for convenient representation of very small lengths.

Conversions and typical uses: 1 Å equals 0.1 nanometers or 100 picometers. Wavelengths of visible light are about 4,000–7,000 Å (400–700 nm), while X-ray wavelengths are typically in the range of roughly 0.5–2 Å. In crystallography, lattice constants are often a few ångströms, and DNA base pairs stack about 3.4 Å apart. Atomic radii for many elements lie on the order of 1–2 Å. Because of its scale, the angström is especially convenient for describing interatomic spacings, crystal structures, and spectroscopic features.

Notation and status: The symbol Å represents the character Angström and is widely used in printed materials; in plain ASCII contexts the unit is often written as angstrom or angström. While SI emphasizes meters and related units, the angström remains common in fields dealing with atomic and molecular dimensions. Some journals and guidelines encourage strict SI usage, but the angström continues to serve as a practical shorthand for nanoscale distances.