Identification at high mass resolution of the positive ion at m/z 19 produced by electron-stimulated desorption: F⁺ (rather than H ₃ O⁺)

Identification at high mass resolution of positive ion at m/z 19 produced by electron-stimulated desorption is presented. Negative ion formation by impact of approximately 100 eV electrons on F-containing molecules occurs primarily by ion-pair formation, for which the cross section is similar to or smaller than that for positive ion formation. It is found that direct electron attachment to a F atom to form F^- has an low cross section, even at low electron energy. Authors also considered electron-stimulated desorption (ESD) of O ⁺ from TiO₂ and advanced a model in which the O, initially residing in the ionic lattice as O^2-, participates in an interatomic Auger transition involving a Ti 2p core level ionized by electron or photon impact. Studies have found that the average kinetic energy of the F²⁺ is twice that of F⁺.