Ion-Impact Energy-Loss Spectrum of Oxygen

Electronic transitions in the oxygen molecule arising from ion—molecule collisions have been studied by measuring the kinetic energy lost by 100 eV–4 keV H+, H2+, and He+ inelastically scattered from O2. The 7–9-eV region of the energy-loss spectrum is strongly collision-energy dependent. The broad feature ordinarily identified as the Schumann—Runge continuum appears to be the result of at least two different transitions. A peak corresponding to the optically forbidden Herzberg continuum (A 3Σu+←X 3Σg −) is observed in all of the ion-impact spectra. Triplet—singlet transitions into the a 1Δg and b 1Σg+ states are the most intense features of the H2+− and He+−impact spectra. Cross sections for the above-mentioned processes exceed 10−17 cm2.