Gross- and Partial-Ionization Cross Sections for Electrons on Water Vapor in the Energy Range 0.1–20 keV

Abstract

Measurements have been made on the gross‐ionization cross sections for 0.1–20‐keV electrons on water vapor at pressures of about 3×10⁻⁴ torr. The results are compared with the cross sections of H₂ and O₂. Within the experimental error of 15% we found no deviations from the additivity rule. The energy dependence of the cross section satisfies the Bethe—Fano—Platzman relation for collision‐induced dipole transitions at energies exceeding 400 eV. A comparison is made with photoionization and inelastic electron‐scattering cross sections. Some results are given on the partial cross sections for the production of fragment ions for 0.02–2‐keV electrons on water vapor.