intraatomic

Intraatomic is an adjective describing phenomena or processes that occur within a single atom. It contrasts with interatomic, which refers to interactions between atoms. The term is used primarily in atomic physics and chemistry to emphasize internal structure and dynamics rather than interactions with other atoms.

Within an atom, intraatomic topics include electronic structure, electron–electron repulsion, and electron–nucleus interactions that shape energy levels and orbital occupations. Intraatomic phenomena also encompass energy-level transitions confined to a single atom, such as electronic transitions responsible for atomic emission or absorption spectra, and the resulting fine and hyperfine structure produced by spin–orbit coupling and nuclear interactions. Other intraatomic considerations involve internal rearrangements of electron density and related perturbations, as well as quantum electrodynamic effects that manifest within the atom.

The term is less common as a standalone label and is often used to clarify that a discussion concerns processes inside one atom rather than between atoms, as in comparisons with interatomic or intramolecular contexts. In some cases, authors may use intraatomic language to highlight details of atomic structure that are independent of chemical bonding or external fields.

See also: atomic physics, spectroscopy, electron configuration, electronic transition, hyperfine structure, spin–orbit coupling, interatomic interactions, intramolecular.

Etymology: from intra- meaning within, and atomicus meaning of the atom.