O−escape during the oxidation of cesium

Abstract

Exposure of Cs surfaces to ${\mathrm{O}}_2$ causes ejection of ${\mathrm{O}}^{\mathrm{-}}$ ions with low yields (∼${10}^{\mathrm{-}8}$ per incident ${\mathrm{O}}_2$ molecule) during the first stages of dissociative chemisorption (followed by exoelectron emission at higher exposures), although the work function of the surface exceeds the electron affinity of O and the energetics of the overall reaction is almost zero. A mechanism is proposed whereafter the release of ${\mathrm{O}}^{\mathrm{-}}$ is a consequence of strong repulsion in ${\mathrm{O}}_2^{2\mathrm{-}}$ species intermediately formed in front of the surface.