Computation and assignment of radial couplings using accurate diabatic data for the LiH molecule

The radial couplings between the 3,1 Sigma + adiabatic states dissociating into Li(2s, 2p, 3s, 3p, 3d, 4s and 4p)+H and Li + +H - are determined from accurate diabatic data. The results are validated by a comparison with previous ab initio calculations. It is shown that the peaks of the radial coupling can be interpreted from the diabatic curves. An over-repulsiveness of the valence diabatic states as compared to the Rydberg diabatic states generates, at short internuclear distances, a series of crossings between neutral diabatic states which are associated with intense peaks of the radial coupling both for the singlet and triplet Sigma states.