MRD-CI-study of the positive molecular ions ArHe+and ArHe2+

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Abstract
The first five 2Σ+ and four 2Π states of ArHe+ are studied by MRD-CI calculations. It is found that various avoided crossings between Rydberg-like and strictly repulsive states occur. The interaction between the B 2Σ+[Ar(1 S) + He+(2 S)] with the higher states predicts the appearance of Ar+ ions in their 3s3p 6, 3s 23p 44s and 3s 23p 43d states at 7·28 eV, 9·38 eV and 11·96 eV respectively; this finding is consistent with appearance potentials for Ar ions at 7·35 eV, 9·3 eV and 10·9 eV derived from observed cross sections in He+-Ar scattering experiments [1]. It is pointed out that calculated data based on single-configuration-type procedures are not satisfactory for a theoretical treatment of charge-exchange reactions. The calculated potential curves for ArHe++ include the first two 3,1Π, three 1Σ+ and one 1Δ, 3Σ+ and 3Σ- states with the dissociation limits Ar+(2 P) + He+(2 S) and Ar++(3 P, 1 D, 1 S) + He(1 S). The interactions between the repulsive Ar+ + He+ and the more bonding Ar++ + He states explain qualitatively the charge transfer reactions between Ar++ and He atoms.