Absolute total electron detachment and relative ionisation cross sections for O₂ ⁻ collisions with O₂ in the energy range (10–1500 eV)

Abstract

Absolute total electron detachment cross for O2- collisions with O2 are reported for impact energies ranging from 10 to 1600 eV as measured with a transmission-beam experimental apparatus. The primary anionic beam projectile is produced in a hollow cathode discharge-induced plasma, and the collisions with the neutral molecular target occur in a gas cell at a well-known constant pressure. In addition, by measuring the time-of-flight (TOF) mass spectra of the positive ions produced during the collisions, the relative total ionisation cross-section for the impact energy range from 90 to 1500 eV has been determined for the first time. The accurate determination of the gas pressure (within 8%) in the scattering chamber allowed us to clarify the important discrepancies (by about a factor 4) prevailing between previous total electron detachment cross-section (TEDCS) measurements. Additional local maxima in the cross-section values, not previously observed, have been detected around 50 and 150 eV.