Interactions of transition metal atoms with He

The adiabatic interaction potentials were obtained for the paradigm transition metal-rare gas interactions: Sc(D-2)-He and Ti (F-3)-He and their di-cations. The ab initio approach included the coupled cluster and multireference configuration interaction methods. He atoms form very weak van der Waals complexes with Sc and Ti with well-depths of ca. 4-5 cm(-1). The interactions are characterized by the nearly-degenerate manifolds of adiabatic states with splittings of the order of 0.1 cm(-1) or less. The anisotropy of the Ti-He interaction is smaller than that for the Sc-He interaction. The origin of the weak anisotropy of these interactions was analyzed. The exchange repulsion was found to be nearly the same in the Sigma, Pi and Delta states due to the valence d-electrons being submerged under the doubly filled 4s electron sub-shell. The anisotropy of the total potential is controlled by the weakly-anisotropic dispersion interaction.