Sr2

Sr2 is the diatomic molecule formed by two neutral strontium atoms. In laboratory settings, it is primarily studied in ultracold or low-temperature gas-phase conditions, where it can be created by photoassociation of ultracold strontium atoms confined in a magneto-optical trap or optical lattice. As a homonuclear diatomic with two heavy alkaline earth atoms, Sr2 exhibits a relatively weak covalent bond and a large internuclear separation compared with lighter diatomics. The ground electronic state is commonly described as X1Σg+.

Spectroscopic investigations of Sr2 map its potential energy curves for the ground and excited electronic states, providing benchmarks for quantum chemistry calculations. The molecule exists in several isotopologue forms, including 84Sr2, 86Sr2, 87Sr2, and 88Sr2, with 87Sr2 featuring nuclear spin I = 9/2, which gives rise to hyperfine structure in the spectra. The study of Sr2 and related dimers helps refine models of bond formation in heavy, closed-shell atoms and informs methods used to produce and manipulate ultracold molecules.

Production and detection techniques for Sr2 typically involve photoassociation of ultracold atoms followed by methods such as resonance-enhanced multiphoton ionization or state-selective imaging to identify molecular states. While Sr2 is not used as a standard reference in timekeeping like atomic strontium clocks, it serves as a valuable system for exploring molecular formation at ultracold temperatures and for testing theoretical approaches to molecular structure and dynamics.