Some energy curves of ArH⁺ and their use in the study of the scattering of H⁺ by Ar

Calculations on the ground state and some excited states of ArH⁺ in the LCAO-STO-MO-SCF approximation are reported. The ground state interaction potential is then used to study the elastic scattering of protons by argon atoms at low and moderate energies. Partial wave calculations involving the JWKB evaluation of the phase shifts are compared to the available experimental results and subsequently used to improve the well depth obtained in the ab initio calculation. The values U=4.3 eV and R_e=1.34 AA are thus found. Qualitative discussions of the approximate excited states lead to the conclusions that the excitation of the argon target, at moderate energies, can take place only via the charge exchange channel-that is, the four lowest monoexcited states of ArH⁺-at R₁ approximately=1 AA. This charge exchange channel being itself coupled to the ground state at internuclear distances 1.70 AA<or approximately=R_x<or approximately=1.85 AA. A tentative explanation of the preferential excitation Ar*(3p⁵ 3d) is given.