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 accurate 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 interplay 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.

Energetics and structural stability of small Hen= 1–6K2+ clusters.

In this theoretical work, we calculate molecular potential energy curves, spectroscopic constants and transition dipole moments for the groundg and first excited electronic states (A 2 Π u ) of alkaline-earth molecular ion + Mg . 2We consider an ab initio multi-reference configuration interaction method using an aug-cc-pv5z Gaussian basis set and compare our results with those obtained by others. The comparison shows a very good agreement. In addition, we investigate the ion-atom elastic collisions for a wide range of energies including the isotopic effect. In close connections, we determine the scattering T-matrix elements for ground-state electronic potentials, which show divergent behavior at a particular energy, indicating the occurrence of scattering resonances. We find that the s-wave scattering length is positive for both ground-state potentials. We also study possible free-bound transitions and Franck-Condon overlap for our system.

Synopsis Doped He droplets constitute an important environment as ultracold homogeneous matrices for spectroscopic studies. Alkali metal dopants have a series of interesting properties due to their unusual bonding behavior. Neutral atoms attached to the surface of the droplet, forming eventually cold molecules via collisions, while charged dopants form solvation shells, related with the low mobility of the ions in experiments. So, investigations on the underlying intermolecular, markedly orientational ionic, forces, and on the miscoscopic structures of alkali-cation-He complexes is essential.