ENERGY AND ANGULAR-DISTRIBUTIONS OF 100-EV TO 400-EV NA+ SCATTERED FROM CU(110)

In this paper we present a detailed analysis of the energy and angular distributions of 100-, 200-, and 400-eV Na+ scattered from the Cu(110) surface. The spectra are analyzed using classical trajectory calculations with an improved ion-surface interaction potential. Qualitative features of the spectra can be reproduced using the chain model. Quantitative agreement between measured and simulated spectra is obtained with full-surface simulations, which include the thermal vibrations of the surface atoms. The trajectories are calculated using a potential constructed from a sum of (Na-Cu)+ Hartree-Fock pair potentials plus an attractive interaction. At lower beam energies, the contribution to the scattering potential from the long-range tails of the pair potentials becomes increasingly important in determining the positions of the rainbow angles. The tails are also responsible for the dramatic increase in "focused" scattering events at lower beam energies. The simulations provide the impact parameters for the detected ions. This information is used to determine the relative importance of zigzag, focused, and top-layer chainlike scattering events. By examining the trajectories of ions scattered into the forward and backward rainbow angles, the extreme sensitivity of the backward rainbow peak to surface thermal vibrations is explained. Lastly, angular spectra from chain and full-surface simulations are compared.