Decay of zero-degree focusing of channeled ions

We present here a study of the effect of zero-degree focusing of C6+ ions moving along the (100) channels of a Si crystal. The ion energy is 25 MeV and the thickness of the crystal is varied from 0 to 5000 atomic layers. The angular distributions of the channeled ions were obtained via the numerical solution of the equations of motion of the ion using the Lindhards expression for the continuum interaction potential, and the computer simulation method. The analysis shows that the effect of zero-degree focusing has a periodic behaviour. It also shows that the maxima of the zero-degree yield of the channeled ions decay with the thickness of the crystal. This decay can be described by a sum of two exponential functions.16th International Conference on Atomic Collisions in Solids (ICACS-16), Jul 17-21, 1995, Linz, Austri