Two-electron pseudopotential investigation of the electronic structure of the CaAr molecule

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The electronic structure of the Ca-Ar molecule is investigated using [Ca2+] and [Ar] core pseudopotentials complemented by core polarization operators on both atoms, considering the molecule to be a two-electron system. The electronic two-body problem is solved by achieving a full configuration interaction with extensive Gaussian basis sets. The potential energy curves and the molecular constants of all CaAr states dissociating into atomic configurations ranging between the ground state 4s2 1S and the doubly excited state 4p2 3P are determined. Spin–orbit coupling is also included in an atom-in-molecule scheme for states dissociating into the 4s4p and 4s3d configurations. The present theoretical results show good overall agreement with experimental data. They also help to clarify the very complicated spectroscopy of the CaAr system in the 38 000 cm−1 energy range where many states correlated with the 4s4d, 3d4p, and 4p2 atomic configurations interact with or cross one another. As a by-product of the present investigation and with the purpose of checking the pseudopotential accuracy on a simpler related system, low-lying potential energy curves of the single active electron CaAr+ ion are also reported and the corresponding molecular constants are compared with the existing literature.