ArgonHelium

Argonhelium refers to a diatomic association between one argon atom and one helium atom. In the language of chemistry, it describes a heteronuclear dimer formed by two noble gas atoms. Unlike typical chemical compounds, Argon and Helium do not form covalent or ionic bonds under ordinary conditions; any Ar–He interaction is governed by weak dispersion (van der Waals) forces.

The Ar–He interaction is very weak and short-ranged. The resulting complex, often described as a van der Waals dimer, does not have a classical chemical bond or a fixed covalent bond length. Instead, it exists as a shallow potential energy minimum with a separational distance of a few angstroms. The binding energy is extremely small, typically a fraction of a wavenumber (on the order of less than a few cm⁻¹), corresponding to microelectronvolt-scale stability. Because of this, Ar–He complexes are usually observed at very low temperatures or in specially prepared environments where collisions are rare.

Formation and observation of argon–helium species occur mainly in cold gas-phase experiments, supersonic expansions, laser spectroscopy, and cryogenic matrices. These studies help characterize weak intermolecular forces between noble-gas atoms and provide insight into quantum effects in van der Waals complexes. Argonhelium is thus not a stable chemical compound in the usual sense but a transient, weakly bound molecular system of interest in physical chemistry and low-temperature physics.