FORCES ON SWIFT IONS NEAR PLANE SURFACES

The electronic response of a semi-infinite medium to a swift point cha rge moving parallel to its surface has been analysed theoretically. Th e aim has been to provide estimates of Stopping power, straggling and lateral deflection of swift ions under grazing incidence on insulating and/or conducting targets. As a byproduct, similar estimates are obta ined for swift ions moving parallel to a thin planar layer which may b e helpful in the analysis of planar channeling at surfaces and in the bulk. The theoretical scheme is based on classical and quantal stoppin g theory in the Impact parameter representation. Symmetry properties h ave been established relating the behavior above the surface plane to the behavior underneath. Well-established results from dispersion theo ry in the long-wavelength limit are reproduced. Those results do not a pply to close collisions and become invalid near the surface. Correcti ons are applied ensuring a correct transition to bulk behavior. The ef fect of excited core electrons which has frequently been neglected is shown to be significant.