Ar2I

Ar2I is a hypothesized binary compound composed of two argon atoms bonded to a single iodine atom. While argon is a noble gas with a closed-shell electron configuration and typically does not form stable chemical bonds, theoretical studies have examined the possibility of Ar–I interactions under extreme conditions. Computational chemistry methods, such as density‑functional theory and coupled‑cluster calculations, suggest that a weak van der Waals complex may exist at very low temperatures or high pressures, but no covalent Ar‑I bond has been confirmed experimentally.

The notation Ar2I is sometimes used in the context of matrix‑isolation spectroscopy, where trace amounts of iodine are trapped in an argon matrix at cryogenic temperatures. In such environments, transient species with characteristic absorption bands have been observed, leading to speculation about a loosely bound Ar2I cluster. These observations are interpreted as physical adsorption rather than true chemical synthesis.

Attempts to generate Ar2I in the gas phase have involved supersonic jet expansions and laser ablation of iodine in an argon carrier gas. While mass‑spectrometric signals corresponding to ArI+ have been detected, the presence of a neutral Ar2I molecule remains unverified. Consequently, Ar2I is considered a theoretical or transient species rather than an isolable compound, and its existence is of interest primarily for understanding noble‑gas chemistry and intermolecular forces.