Resonantlike desorption of negative ions by core-level excitation under electron bombardment

Electron-stimulated desorption of positive and negative hydrogen ions from hydrogenated GaAs surfaces has been studied as a function of impact electron energy. Well-defined peaks in the negative ion yield are observed at incident electron energies close to Ga and As core-level binding energies, suggesting that resonantlike core-level electronic transitions involving matrix atoms are most likely responsible for such behavior. We propose that the formation and subsequent breakup of superexcited molecular complexes containing a core hole can lead directly to the ejection of negative ions.