Orientation dependence in electron capture to arbitrary projectile n states from molecular hydrogen

The dependence on the orientation of the intermolecular axis of cross sections for electron capture from molecular hydrogen by bare ions is calculated in a two-center approximation, which ignores multiple scattering between atomic centers and is compared to experiment. Electron-capture cross sections are calculated as functions of both projectile principal quantum number n and molecular orientation angles. Orientation-averaged cross sections are compared with recent measurements of O⁸⁺+H₂ at E=8, 10, 12.5, 16, and 20 MeV. Comparisons are also made between our calculations for electron capture into projectile n states by H⁺ from H₂ and the available calculation for ns states from E=50 keV to 5 MeV. The orientation-dependence differential in the molecular-orientation angle is studied in dissociative ionization and excitation of the molecular ion following single-electron capture from H₂ using a two-step independent-electron model. The calculated orientation dependence is in qualitative agreement with preliminary experimental observations as a function of the orientation angle done with O⁸⁺ ions at E=10 MeV, where capture to n>1 state is significant.