Abstract. A modulated crossed-beam technique has been used to study the ionization of potassium and sodium vapour by 20-100 keV H⁺ and He⁺ ions. Absolute cross sections sigma _e for electron production have been determined from the gross yield of electrons. Mass spectrometric measurements of the relative abundance of secondary ion species, together with measurements (in a subsidiary experiment) of the total one-electron capture cross section sigma ₁₀ have been used to determine cross sections for Na⁺, K⁺, and K²⁺ formation. Proton impact ionization cross sections are shown to be in generally poor accord with theoretical estimates based on both the classical impulse and Born approximations.

Print publication: Issue 18 (21 December 1975)