Ionization of Inert Gases by Positive Potassium Ions

Ionization of the inert gases by relatively low-energy potassium ions has been investigated. The use of relatively intense ion beams and phase-sensitive detection of ionization signals yields a large increase in sensitivity over that obtained in former investigations. The enhanced sensitivity permits detection of ionization at lower ion energies than heretofore reported. Evidence is presented for a real ionization threshold potential for ${\mathrm{K}}^{+}$ ions in Kr.