ONE-ELECTRON CAPTURE IN COLLISIONS OF 6-100 KEV PROTONS WITH OXYGEN-ATOMS

A crossed-beam technique incorporating time-of-flight analysis and coi ncidence counting of the collision products has been used to study one -electron capture by 6-100 keV protons in collisions with oxygen atoms . In these measurements, ground-state oxygen atoms were provided by an iridium tube furnace dissociation source. The measurements extend the energy range of previous experiments and, for the first time, provide separate cross sections (10)sigma(01) for the simple charge transfer process (which is dominated by accidentally resonant one-electron capt ure) and (10)sigma(02) for the transfer ionization process leading to O2+ formation. The present cross sections were obtained using a techni que and normalization procedure different from all previous measuremen ts. In particular, our measured values of (10)sigma(01) are in good ac cord with previous 0.04-10 keV data by Stebbings er al based on a modu lated crossed-beam technique but at variance with the considerably sma ller values in the range 2.5-25 keV obtained by Williams et al using a furnace target method. While our values of (10 sigma 01) decrease wit h increasing energy over the range considered, transfer ionization cro ss sections pass through a peak value at 34 keV where this process acc ounts for about 9% of the total one-electron capture cross section ris ing to 17.5% at 100 keV.