Optical Stark spectroscopy of the A˜2Πr (0 0 0) ← X˜2Σ+ (0 0 0) system of barium monohydroxide, BaOH

► Permanent electric dipole moment of barium monoxide. ► Assessment of semi-empirical bonding models. ► Optical Stark effect in BaOH. ► Comparison of bonding in of hydroxides and halides.