Absolute differential and integral cross sections for charge transfer of keV O+ ions with O-2

We report measurements of the absolute differential cross sections for char ge-transfer scattering of 0.5-, 0.85-, 1.5-, 2.8-, and 5-keV O+ ions by O-2 at scattering angles between 0.04 degrees and 5.4 degrees in the laborator y frame. Cross sections for both O+(S-4) ground-state and O+(D-2,P-2) metas table ions are presented. The metastable differential cross section is some what more forward peaked than that for the ground state. Integral and total cross sections are also reported. The present O+(S-4) cross section is con sistent with previous measurements, but the present metastable-state cross section is found to be substantially lower than previously reported in this energy range. These measurements provide information relevant to model cal culations of O+ precipitation into the upper atmosphere during geomagnetic storms.