Secondary-Electron Emission from Molybdenum Due to Positive and Negative Ions of Atmospheric Gases

Secondary-electron yields from a clean surface of Mo have been measured for H⁺, H₂⁺, H₃⁺, H^-, O⁺, O₂⁺, O^-, O₂^-, N⁺ and N₂⁺ in the kinetic energy range 40 eV to 2 keV. These measurements have been made under ultrahigh vacuum of order 10^-10 Torr. The rate of variation of the electron yield γ with kinetic energy of the incident ion decreases as the ion mass increases, consistently from H⁺ to O₂⁺. Evidence is presented to show that kinetic emission is much less affected by monolayer coverage of the surface than potential emissions is. For clean surfaces, the negative-ion yields represent most closely the kinetic-emission characteristics of the bombarding particles.