84Sr2

84Sr2 is a homonuclear diatomic molecule formed from two atoms of the isotope strontium-84 (84Sr). Strontium-84 is a stable isotope of strontium, which has several naturally occurring isotopes; 84Sr has a natural abundance of about 0.5–0.6%. As a diatomic consisting of identical atoms, 84Sr2 belongs to the family of strontium dimers (Sr2) and has isotopologues such as 86Sr2 and 88Sr2 as alternatives used in comparative studies.

Electronic structure and bonding: The ground electronic state of Sr2 and its isotopologues is typically described as X1Σg+. The bonding in Sr2 is weak and governed largely by van der Waals dispersion forces, leading to a relatively long bond length and small binding energy compared with many covalently bonded molecules. The potential energy surface is sensitive to the reduced mass of the molecule, which for 84Sr2 differs slightly from other isotopologues and affects vibrational and rotational spectra.

Production and spectroscopy: 84Sr2 has been investigated in ultracold-atom experiments where atoms of 84Sr are laser-cooled and assembled into weakly bound molecules via photoassociation. Spectroscopic studies near the dissociation limit resolve vibrational levels and provide tests of ab initio potential energy curves. Isotopic substitution shifts vibrational spacings and rotational constants, offering a stringent check on theoretical models.

Significance: Studying 84Sr2 alongside other Sr2 isotopologues helps benchmark high-accuracy quantum chemistry for heavy alkaline-earth dimers, informs understanding of long-range dispersion forces, and supports precision metrology contexts that use strontium-based systems and optical clocks.

See also: Strontium, Sr2, strontium isotopes, ultracold molecules.