Charge transfer of keV O+ ions with atomic oxygen

We report absolute differential cross sections for charge transfer scatteri ng of 0.5-5 keV O+(S-4) ground state and O+(D-2, P-2) metastable ions by at omic oxygen at angles between 0.04 degrees and 3 degrees in the laboratory frame. Absolute total charge transfer cross sections, derived from these me asurements, are compared with previously published data. The measurements w ere made using a flowing gas target, which consisted of a mixture of atomic and molecular oxygen produced by passing O-2 through a microwave discharge . The atomic oxygen cross sections were obtained by appropriate subtraction of the signal due to molecular oxygen from that due to the mixture of O an d O-2. These data are relevant to model calculations of energetic O+ precip itation into the upper atmosphere and to the diffusion of low-energy O+ ion s in the ionosphere.