87Sr2

87Sr2 is a homonuclear diatomic molecule consisting of two 87Sr atoms, the fermionic isotope of strontium with nuclear spin I=9/2. It is an isotopologue of the diatomic Sr2 and, like other Sr2 species, is a weakly bound van der Waals molecule that can exist in the electronic ground state and low-lying excited states. In the ground electronic state, the molecule has X1Sigma_g+ symmetry. The presence of two fermionic nuclei endows 87Sr2 with rich hyperfine structure in its ro-vibrational levels.

Production and study in the laboratory are part of ultracold-atom research. 87Sr atoms are prepared in quantum-degenerate or near-degenerate samples and bound pairs are created using optical association techniques, typically on the narrow 1S0–3P1 intercombination line around 689 nm. Magnetic Feshbach resonances are weak in strontium; optical methods are favored. Resulting molecules can be detected by molecule-induced loss, dissociation back to atoms, or resonance-enhanced multiphoton ionization.

Spectroscopic studies of 87Sr2 map out potential energy curves, long-range interactions, and hyperfine couplings. The isotope’s nuclear spin leads to multiple hyperfine components, enabling detailed tests of ab initio and coupled-channel calculations. Knowledge of 87Sr2 helps constrain interatomic potentials for Sr atoms, informs studies of quantum chemistry in heavy-atom systems, and supports research in precision measurement and quantum simulation with ultracold molecules. 87Sr2 coexists with other Sr2 isotopologues, such as 84Sr2, 86Sr2, and 88Sr2, which lack nuclear spin or have distinct hyperfine structures.