Absolute partial cross sections for electron-impact ionization ofH2,N2, andO2from threshold to 1000 eV

Abstract

Absolute partial cross sections from threshold to 1000 eV are reported for electron-impact ionization of ${\mathrm{H}}_{2}$, ${\mathrm{N}}_{2}$, and ${\mathrm{O}}_{2}$. Data are presented for the production of ${\mathrm{H}}_{2}^{\mathrm{}+}$ and ${\mathrm{H}}^{+}$ from ${\mathrm{H}}_{2}$; the production of ${\mathrm{N}}_{2}^{\mathrm{}+}$, ${\mathrm{N}}^{+}$+${\mathrm{N}}_{2}^{\mathrm{}2+}$, and ${\mathrm{N}}^{2+}$ from ${\mathrm{N}}_{2}$; and the production of ${\mathrm{O}}_{2}^{\mathrm{}+}$, ${\mathrm{O}}^{+}$+${\mathrm{O}}_{2}^{\mathrm{}2+}$, and ${\mathrm{O}}^{2+}$ from ${\mathrm{O}}_{2}$. 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 \ifmmode\pm\else\textpm\fi{}3.5% and is marginally higher for fragment ions. Previous cross-section measurements are compared to the present results. \textcopyright{} 1996 The American Physical Society.