Neutral and ionic dopants in helium clusters: Interaction forces for the Li₂ (a³Σ_u⁺-He and Li ₂⁺ (X²Σ_g⁺-He complexes

The potential energy surface (PES) describing the interactions between and 4 He and an extensive study of the energies and structures of a set of small clusters, Li 2 (He) n, were reported in a previous series of publications. In the present work, the same analysis is extended to the case of the excited and of the ionized Li moiety. Calculated interaction potentials for the two title systems and the corresponding fitting of the computed points are shown. For both surfaces the MP4 method with cc-pV5Z basis sets has been used to generate an extensive range of radial/angular coordinates of the two-dimensional PESs which describe rigid rotor molecular dopants interacting with one He partner.