On the surface-normal energy distribution of sputtered recoils

It is shown that, if the recoil-energy distribution in front of a bombarded target is of the form 2Esub(e) (Esub(e)+U)-3dEsub(e), where U is the surface binding energy, then the corresponding surface-normal distribution is (E + U)-2dE. This being so, it is fairly straightforward to deduce the integral yield of sputtered ions or excited states, including allowance for electron exchange with the solid. Also treated are the integral and differential yields of sputtered excited states as a function of perpendicular distance from the target, as would be relevant if the photons from the excited states were detected over an edge (integral case) or through a slit (differential case). Curves of yield vs. distance should show a marked concave-upwards curvature on a semi-logarithmic plot, a result which is well-known experimentally. (author)