Quantum features of anionic species He*− and He2*− in small HeN clusters

9 págs.; 11 figs.; 2 tabs.; Published as part of The Journal of Physical Chemistry A virtual special issue “Spectroscopy and Dynamics of Medium-Sized Molecules and Clusters: Theory, Experiment, and Applications”.We present variational calculations on systems containing a few boson helium atoms attached to electronically excited atomic and molecular helium anions He*– and He2*– and characterize their structures and energetics. Previously reported high-level ab initio results [Huber, S. E.; Mauracher, A. Mol. Phys. 2014, 112, 794] to describe the interactions between excited (metastable) anions and a neutral He atom have been employed. For the case of the atomic species He*–, the corresponding interaction with He suggests large anharmonicity effects due to the presence of a deep well of ∼17 500 cm–1 at short distances, together with a more external shallow secondary well of ∼4 cm–1, both supporting bound levels. Moreover, when a sum of pairwise interactions is assumed to describe the full PES corresponding to the presence of several neutral He atoms, geometrical constraints already predict the complete solvation of the anionic impurity by six helium atoms, giving rise to a bipyramidal structure. In turn, for the anisotropic weak interaction He–He2*–, where the anionic dimer is considered as a rigid rotor, the obtained structures show the tendency of the helium atoms to pack themselves together and largely far away from the dopant, thereby confirming the heliophobic character of He2*–.The authors thank the Centro de Calculo (IFF), CTI (CSIC), and Centro de Supercomputacion de Galicia (CESGA) for allocation of computer time. This work has been supported by MICINN, Spain, Grants FIS2011-29596-C02-01 and FIS2014- 51933-P. F.A.G. acknowledges several helpful discussions with A. Mauracher and thanks him for providing us with the original computed ab initio points for the He−dopant interactions. The aid of COST Action CM1405 (MOLIM) is also acknowledged.Peer Reviewe