COLLISIONS OF AR+ IONS WITH SURFACE CU ATOMS AND CHARGE EXCHANGE OF SCATTERED IONS NEAR METAL SURFACE

Absolute intensities of scattered projectile and recoil ions resulting from large-angle collisions of 60 and 90 keV Ar+ ions in a (100) surface of a solid Cu target are presented. These intensities are studied as a function of scattering angle and also as a function of the angle between the direction of emerging ions and the surface. A model is proposed which interrelates the observed ion yields in the cases of ion-surface atom scattering and ion-gas atom scattering. This model describes the collision of an ion with a surface atom in two phases. The first phase essentially neglects any interaction of the two collision partners with the metal surface and therefore is exactly the same as the model to describe ion-free atom collisions. The second phase starts after the moment that ion formation has taken place and consists of a continous interaction of the scattered ions with the surface on their path to the analyzer. The interaction is assumed to be charge exchange of the ions by capture of metal electrons. These processes are found to have rates of about 1015/s depending on charge state and metal-ion distance. © 1969.