Temperature-dependent scattering of hyperthermal energy K⁺ ions

Extensive experimental and theoretical results are presented for the scattering of a beam of K⁺ ions incident on a Cu(001) surface along the ⟨100⟩ azimuth with incident energies of 50 to 154 eV. Energy-resolved scattered intensity spectra reveal three distinct peaks whose widths and intensities vary with surface temperature. Using the results of a classical trajectory simulation, four distinct ionic trajectory types are assigned to these peaks. Using a classical mechanical theory that contains the correct equilibrium thermodynamics of the Cu crystal, general features of the K⁺ energy-resolved spectra are calculated for each trajectory type and compared with the experimental results. For the case of single ion-surface atom collisions, the dependence of the peak intensities and widths on the incident energy and surface temperature is well explained by the classical theory.