Ab-initio calculation of the ground and excited states of MgH using a pseudopotential approach

The electronic structure of the MgH molecule is investigated using a pseudopotential description of the Mg 2 + core, complemented by a core polarization operator. The electronic problem is treated by the Internally Contracted Multi-Reference Configuration Interaction method (IC-MRCI). The potential energy curves and the molecular constants are calculated for all MgH molecular states dissociating up to the excited atomic configurations Mg(3s3d1D) + H(1s2S). A good agreement with the available experimental data is found. These calculations help to clarify the very complicated spectroscopy of MgH in the 35 000–46 000 cm - 1 excitation range, where many states correlated with the 3s3p, 3s4s and 3s3d atomic configurations cross one another. For instance, the predissociation mechanism of the B 2 Σ + state is enlighten. Both the doublet and quartet systems are documented.