Alignment effects in charge transfer and excitation for H⁺ and He²⁺ collisions with H₂⁺

The excitation and charge transfer cross sections are calculated for the collision of H⁺ and He²⁺ with H₂⁺ molecular ions. This is the simplest example of collisions between ions and molecules or molecular ions since it involves only one electron. The results in this paper emphasize effects due to the alignment of the axis of the H₂⁺ molecular ion relative to the atomic ion velocity vector and due to the internuclear separation. The calculations show that the cross section versus the angle between the molecular ion axis and the ion velocity vector strongly depends on the ion velocity. Our results for He²⁺ collisions do not agree with the experiments and calculations of Reiser, Cocke and Bräuning Phys. Rev. A 67 062718 (2003)] but are in qualitative agreement with the calculations of Cheng and Esry.