First-principle interaction potentials for metastable He(3S) and Ne(3P) with closed-shell molecules: Application to Penning-ionizing systems

We present new interaction potential curves, calculated from first-principles, for the He(S-3, 1s(1)2s(1))center dot center dot center dot H-2 and He(S-3)center dot center dot center dot Ar systems, relevant in recent Penning ionization experiments of Henson et al. [Science 338, 234 (2012)]. Two different approaches were applied: supermolecular using coupled cluster (CC) theory and perturbational within symmetry-adapted perturbation theory (SAPT). Both methods gave consistent results, and the potentials were used to study the elastic scattering and determine the positions of shape resonances for low kinetic energy (up to 1 meV). We found a good agreement with the experiment. In addition, we investigated two other dimers composed of metastable Ne (P-3, 2p(5)3s(1)) and ground state He and Ar atoms. For the Ne(P-3)center dot center dot center dot He system, a good agreement between CC and SAPT approaches was obtained. The Ne(P-3)center dot center dot center dot Ar dimer was described only with SAPT, as CC gave divergent results. Ne* systems exhibit extremely small electronic orbital angular momentum anisotropy of the potentials. We attribute this effect to screening of an open 2p shell by a singly occupied 3s shell. (C) 2013 AIP Publishing LLC.