Zeeman effect

Zeeman effect, changes in the energy levels of atoms that may be observed by the splitting of spectral lines when a light source is placed in a magnetic field. The line separations are expressed as differences of frequency and increase in direct proportion to the strength of the magnetic field. They occur when an atom's electron moves from one energy level, corresponding to the concentric orbits the electron makes around the atomic nucleus, to another. The effect was discovered (1896) by Pieter Zeeman, a Dutch physicist, and was the first indication that electrons are negatively charged particles. It is used by astronomers and physicists to study the properties of nuclei, atoms, and molecules.

See also: Atom; Electron.