Theoretical Study of Cationic Alkali Dimers Interacting with He: Li2+-He and Na2+-He van der Waals Complexes.

Abstract

We present a theoretical study on the potential energy surface and bound states of He-A+2 complexes, where A is one of the alkali Li or Na atoms. The intermolecular interactions was systematically investigated by high-level ab initio electronic structure computations, and the corresponding raw data were then employed to reproduce accu- rate analytical expressions of the potential surfaces. In turn, we used these potentials to evaluate bound configurations of the trimers from nuclear quantum calculations, and extract information on the effect of orientational anisotropy of the forces and the in- terplay between repulsive and attractive interaction within the potential surfaces. The spatial features of the bound states are analyzed and discussed in detail. We found that both systems are going under large amplitude stretching and bending motions with high zero-point energies. Despite the large differences in the potential well-depths, the correct treatment of nuclear quantum effects provides insights on the effect of different strength of the ionic interaction on the spectral structure of such cationic alkali van der Waals complexes, related with the mobility of ions and the formation of cold-molecules in He-controlled environments.