Observation of low-energy Z oscillations in total electron-capture cross sections for bare projectiles colliding with H and H2

An oscillatory charge dependence of total electron-capture cross sections has been observed for fully stripped projectiles having charge 6< or =Z< or =10 incident on H and H2 at collision energies below 3.0 keV/amu. The oscillations are attributed to the discreteness of the projectile final-state spectrum and the strong selectivity of the capture process at a given energy. Relative maxima in the cross sections occur for odd projectile charge in the case of H, and for even projectile charge in the case of the H2 target. This shift is explained in terms of a Landau-Zener curve-crossing picture of the electron-transfer collision