Electron Transfer and Detachment in Collisions of Low-Energy Negative Ions with O2

Total cross sections for the production of slow heavy negative ions and of free electrons in collisions of O₂⁻, O⁻, OH⁻, and H⁻ ions with O₂ molecules have been measured over the primary‐ion KE range from a few electron volts to 350 eV. The experiments are of the ion‐beam gas‐scattering type and utilize a radio‐frequency filter to give separately the currents of detached electrons and slow product negative ions. The cross sections for slow ion formation, ${\sigma }_t$ , were appreciable at all energies studied, for all four collision systems. The dominant contributions to ${\sigma }_t$ could in most cases be attributed to simple charge transfer, although in the H⁻–O₂ and OH⁻–O₂ systems at low energies, the data indicate that ion–molecule reactions also contribute. With exception of the H⁻–O₂ system, the electron detachment cross sections were similar in magnitude and in behavior with collision energy to those which have been measured previously for other systems.