ESD of H+ and D+ by a two-electron process from hydrogen adlayers on Pt(1 1 1)

The electron stimulated desorption (ESD) behavior of H+ and D+ from a Pt(1 1 1) surface covered with dissociatively adsorbed hydrogen or deuterium has been investigated. Incident electron energies of 150 eV caused both the H+ and D+ ion yields to initially increase before finally decaying away. The position of the ion-yield maximum in the ion-yield curves exhibits a strong dependence on electron-beam current density, but little dependence on the initial H2 or D2 exposures. Ion yield is seen to increase quadratically with electron-beam current density, indicating that ESD of H+ and D+ is a two-electron process. Kinetic energy distributions (KED) were also investigated. Comparison of the H+ and D+ ESD KED spectra clearly shows that the peak position for H+ KED is lower than that for D+ KED, and that H+ KED broaden to lower kinetic energy relative to D+ KED. The Menzel-Gomer-Redhead (MGR) model is used to develop a possible qualitative explanation of the differences observed in the ESD behavior for H+ and D+ . Total removal cross-sections were also measured for adsorbed hydrogen and deuterium, for which current density averaged cross-sections of QH=(1.6±0.1)x10-16 cm2 and QD=(1.3±0.2)x10-16 cm2 were obtained