IONIZATION OF ATOMIC OXYGEN BY PROTONS

A crossed-beam technique incorporating time-of-flight analysis and coi ncidence counting of the collision products, recently used in this lab oratory to study one-electron capture in collisions of H+ ions with gr ound-state oxygen atoms, has been adapted to allow measurements of the corresponding cross sections for ionization for the first time. Cross sections for the single ionization of O atoms have been determined wi thin the range 34-100 keV. These cross sections pass through a peak va lue at an energy of about 60 keV. At higher energies, the process of i onization rather than electron capture becomes the main source of O+ p roduction. O+ formation for n > 2 was too small to detect in the energ y range considered. It is also shown that although production of O2+ t hrough transfer ionization is quite significant. the yield of O2+ from pure ionization is unimportant.