Isotope Effect in Electron Stimulated Desorption: Oxygen Chemisorbed on Tungsten

Abstract

Electron stimulated desorption (ESD) studies of oxygen chemisorbed on tungsten have revealed a large isotope effect in the desorption of ions. The probability of desorption of ¹⁶O⁺ was found to be a factor of ∼1.5 greater than the probability of desorption of ¹⁸O⁺ upon bombardment of the adsorbed layer by 100‐eV electrons. This observation is quantitatively consistent with the ESD mechanism proposed independently by Redhead and by Menzel and Gomer. On the other hand, the small isotope effect observed in ESD “total” desorption does not agree with this mechanism; possible reasons for this are discussed.