Absolute partial cross sections for electron-impact ionization of H-2, N-2, and O-2 from threshold to 1000 eV

Absolute partial cross sections from threshold to 1000 eV are reported for electron-impact ionization of H-2, N-2, and O-2 Data are presented for the production of H-2(+) and H+ from H-2; the production of N-2(+), N+ + N-2(2+), and N2+ from N-2; and the production of O-2(+), O+ + O-2(2+), and O2+ from O-2 The product ions are mass analyzed with a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output provides clear evidence that all energetic fragment ions are collected. The overall uncertainty in the absolute cross-section values for singly charged parent ions is +/-3.5% and is marginally higher for fragment ions. Previous cross-section measurements are compared to the present results.