Orientation dependence in electron capture to arbitrary projectilenstates 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.