The scattering of ions by a clean surface in the 1 to 10 eV range. ch. 2

A surface model is proposed which consists of partially screened spherical caps oscillating in a direction normal to the undisturbed surface to correlate measurements of the trapping probability of sodium and potassium ions on clean (110) tungsten surfaces at energies of 1 to 15 eV and incidence of 100 to 700 from the normal to the surface. The trapping probability may be represented as a relatively simple function of angle, mass ratio, surface temperature and beam energy to ionization potential ratio, with good agreement with experimental data. The model depends on some assumptions about elevation and azimuthal screening of lattice sites which cannot fully be justified from first principles. (Auth.)