Neutral and ionic dopants in helium clusters: interaction forces for the   $Li_2(a^3\Sigma_u^+)-He$ and $Li_2^+(X^2\Sigma_g^+)-He$
  The potential energy surface (PES) describing the interactions between $\mathrm{Li_{2}(^{1}\Sigma_{u}^{+})}$ and $\mathrm{^{4}He}$ and an extensive study of the energies and structures of a set of small clusters, $\mathrm{Li_{2}(He)_{n}}$, have been presented by us in a previous series of publications [1-3]. In the present work we want to extend the same analysis to the case of the excited $\mathrm{Li_{2}}(a^{3}\Sigma_{u}^{+})$ and of the ionized Li$_{2}^{+}(X^{2}\Sigma_{g}^{+})$ moiety. We thus show here calculated interaction potentials for the two title systems and the corresponding fitting of the computed points. 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 PES's which describe rigid rotor molecular dopants interacting with one He partner. 
E. Bodo (1), F. A. Gianturco (1), E. Yurtsever (2), M. Yurtsever (3)   ((1) Dept. of Chemistry and INFM, University of Rome ...