Trajectory analysis of low-energy and hyperthermal ions scattered from Cu(110)

We have investigated the trajectories of ${\mathrm{Na}}^{+}$ ions scattered from the Cu(110) surface in the 〈11¯0〉 and 〈001〉 azimuths for a range of incident energies from 56 eV to 4 keV. Our goal is to explain the trends observed in the energy spectra and determine what types of trajectories contribute to these spectra. Using the computer program SAFARI, we have performed simulations with trajectory analyses for 100-, 200-, and 400-eV scattering. We show results from the 100-eV simulations in both azimuths and compare them with the experimental data. The simulated energy spectra are in excellent agreement with the data. Ion trajectories and impact parameter plots from the simulations are used to determine the relative importance of different types of ion–surface-atom collisions. The simulations have shown that the striking differences observed in comparing the 〈11¯0〉 and 〈001〉 spectra are mostly due to ions which scatter from second-layer atoms. This system exhibits strong focusing onto the second-layer atoms by the first-layer rows, and the focusing is very sensitive to the spacing between the rows. At the lower beam energies, scattering from the second layer dominates the measured spectra.