Electric dipole moments and chemical bonding of diatomic alkali–alkaline earth molecules

We investigate the properties of alkali–alkaline earth diatomic molecules in the lowest Σ+ states of the doublet and quartet multiplicity by ab initio calculations. In all sixteen cases studied, the permanent electric dipole moment points in opposite directions for the two spin states. This peculiarity can be explained by molecular orbital theory. We further discuss dissociation energies and bond distances. We analyze trends and provide an empirically motivated model for the prediction of the permanent electric dipole moment for combinations of alkali and alkaline earth atoms not studied in this work.