Transmission of low-energy oxygen ions through ultrathin rare-gas films: Molecular-dynamics simulation

By use of molecular dynamics we simulate a recent experiment by Sack et al. in which oxygen ions are desorbed by electron impact from a ${\mathrm{WO}}_{\mathit{x}}$ surface, and their transmission through rare-gas films of a few monolayer thickness has been measured. When using only elastic scattering cross sections between ${\mathrm{O}}^{+}$ and rare-gas atoms in the simulation, we find fair quantitative agreement with the measured transmission yield, and energy, and angular distributions, for Xe and Kr films. The large number of transmitted oxygen ions can be traced back to the small ${\mathrm{O}}^{+}$ radius. The discrepancy between measured and simulated transmission behavior through Ar films is attributed to either electronically inelastic losses or structural effects in these films. The im pact of this work on the depth of origin of sputtered particles is discussed.