Hyperfine structure of ${}^2\mathrm{\Sigma }$ molecules containing alkaline-earth-metal atoms

Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF, and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth-metal and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

Figure 1

Zeeman splitting of the lowest hyperfine energy levels of ${}^{87}\mathrm{Rb}{}^{88}\mathrm{Sr}$ for magnetic fields up to 20 G.