Absolute Cross Sections for Direct and Dissociative Ionizations of Oxygen Molecule Measured by 350–8000 eV Electron Impact

The direct and dissociative ionizations of oxygen molecule are investigated experimentally by electron collision with energies from 350 eV to 8000 eV. The absolute ionization cross sections for the product ions (\rmO_2^ +, \rmO_2^2 + , O⁺, O²⁺, and their total) and two Coulomb explosion channels (O⁺+O⁺ and O²⁺+O⁺) are obtained by putting the data of O₂⁺ on the scale of Ar⁺ from O₂ and Ar gases mixed with a fixed relative flow ratio of 1:1. The experimental errors are assessed by taking uncertainties of various factors into account. The present absolute cross sections are well consistent with the previous data in the overlapped energy range below 1000 eV.