The electronic structure of the alkaline-earth-atom (Ca, Sr, Ba) hydride molecular ions

The main electronic properties, namely potential energy curves, permanent and transition dipole moments, static dipole polarizabilities, of the alkaline-earth hydride ion SrH+, as well as of CaH+ and BaH+ are computed through a full configuration interaction performed in a two-valence electronic configuration space build from a large Gaussian basis set. The doubly charged ionic core of the alkaline-earth atoms is modelled by an effective core potential including core polarization effects. Our study confirms that the properties of these series of molecular ions have very similar patterns, while it is predicted that the major electronic transition between the electronic ground state and the lowest excited state in BaH+ is significantly weaker than the one in CaH+ and SrH+. Such a study represents a first step towards the modelling of reactive collisions between cold and trapped alkaline-earth ions and H2, as well as for precision measurements based on overtone transitions using cold molecular ions.