Interactions of C+(2 ) with rare gas atoms: incipient chemical interactions, potentials and transport coefficients

Accurate interatomic potentials were calculated for the interaction of a singly charged carbon cation, C⁺, with a single rare gas atom, RG (RG = Ne-Xe). The RCCSD(T) method and basis sets of quadruple-ζ and quintuple-ζ quality were employed; each interaction energy was counterpoise corrected and extrapolated to the basis set limit. The lowest C⁺(²P) electronic term of the carbon cation was considered, and the interatomic potentials calculated for the diatomic terms that arise from these: ²Π and ²Σ⁺ Additionally, the interatomic potentials for the respective spin-orbit levels were calculated, and the effect on the spectroscopic parameters was examined. In doing this, anomalously large spin-orbit splittings for RG = Ar-Xe were found, and this was investigated using multi-reference configuration interaction calculations. The latter indicated a small amount of RG → C⁺ electron transfer and this was used to rationalize the observations. This is taken as evidence of an incipient chemical interaction, which was also examined via contour plots, Birge-Sponer plots and various population analyses across the C⁺-RG series (RG = He-Xe), with the latter showing unexpected results. Trends in several spectroscopic parameters were examined as a function of the increasing atomic number of the RG atom. Finally, each set of RCCSD(T) potentials was employed, including spin-orbit coupling to calculate the transport coefficients for C⁺ in RG, and the results were compared with the limited available data.This article is part of the theme issue 'Modern theoretical chemistry'.