ELECTRON-STIMULATED DESORPTION VIA DISSOCIATIVE ATTACHMENT IN AMORPHOUS H2O

Low energy (0-12 eV) electron impact on condensed amorphous H2O and D2O films is shown to induce electron stimulated desorption of H- and D-, respectively, via dissociative electron attachment. The onsets for H- and D- detection are at 5.5 eV, with a maximum yield for anion desorption at approximately 7.4 eV. The kinetic energy distributions of the desorbing anions are peaked near 0 eV, indicating that the anions suffer post-dissociation collisions at or near the surface, with a large probability of anion trapping on the surface. The present results provide direct information on the dissociation products, prior to the interferences of subsequent reaction processes in the condensed film.