Cross sections for ionization of gases by 5-4000-keV protons and for electron capture by 5-150-keV protons

Using the parallel-plate-capacitor method and a capacitance manometer to determine pressures, total cross sections for the production of positive and negative charges were measured for 5-4000-keV-proton impact on He, Ne, Ar, Kr, ${\mathrm{H}}_2$, ${\mathrm{N}}_2$, CO, ${\mathrm{O}}_2$, C${\mathrm{H}}_4$, and C${\mathrm{O}}_2$. From these, ionization and electron-capture cross sections were obtained and fitted to semiempirical equations describing the energy dependence in terms of a few parameters. At high energies very good agreement is obtained in the comparison of the ionization cross sections to earlier proton- and electron-impact measurements and with theoretical treatments where they are available, but discrepancies exist for some targets at low energy. Above 10 keV the electron-capture cross sections are in agreement with earlier work for all the targets except CO and C${\mathrm{H}}_4$ for which they are (20-40)% higher.