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

Abstract

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 H 2 or D 2 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 Q H=(1.6 ± 0.1) × 10 −16 cm 2 and Q D=(1.3 ± 0.2) × 10 −16 cm 2 were obtained.