Deduction of the He-Fe interaction potential in eV-range from experimentaldata by computer simulation in grazing ion-surface scattering: Row-model

In glancing-angle scattering of keV-ions from a crystal surface, the ion re flection takes place in the eV-part of the interaction potentials. The elas tic interactions are determined by the energy transverse to atomic rows, wh ich can be of the order of 10 eV, A row-model using averaged potentials acc ording to the Lindhard cylindrical potential has been developed using step- by-step integration of Newton's equations of motion. Previously [D. Danailo v, K. Gartner, A. Care, Nucl. Instr. and Math. B 153 (1999) 191; presented on COSIRES, Okayama, 1998] we reported that zig-zag trajectories within sur face channels and the corresponding multimode azimuthal angular distributio ns of reflected ions are very sensitive to the interaction potential used i n the simulation. Here we simulate the scattering of 15 keV Heatoms from Fe (1 0 0) surfaces at different angles of incidence comparable with previousl y published experimental results [D, Danailov, T. Igel, R. Pfandzelter, H. Winter, Nucl. Instr. and Meth. B 164-165 (2000) 583]. Our results show that for interaction energies below about 4 eV the well-known "universal" poten tial works well. However. for energies between 4 and 13 eV the "individual" He-Fe potential(D. Danailov, K. Gartner, A. Care, Nucl. Instr. and Meth. B 153 (1999) 191, presented on COSIRES, Okayama, 1998) gives a better agreem ent with the experimental data. For interaction energies above 13 eV both p otentials are similar. We have constructed a mixed He-Fe potential, which d escribes the experimental observations well. The row-model enables us to de duce the He-Fe interaction potential in the eV-range. In addition, a shift in the experimental angular spectra compared with the calculated spectra in dicates that the atomistic rows undergo an elastic horizontal bend due to t he scattering and an order of magnitude smaller vertical displacement. (C) 2001 Elsevier Science B.V. All rights reserved.