Zero-degree focusing of channeled ions and crystal rainbows

We analyze here theoretically the connection between the effect of zero-deg ree focusing of channeled ions and the crystal rainbow effect. The calculat ions were performed for Ne10+ ions and a < 100 > Si thin crystal. The ion e nergy was 60 MeV and the crystal thickness was varied between 630 and 750 a tomic layers. These conditions correspond to the neighborhood of the first maximum of the zero-degree yield of the channeled ions. The obtained result s show that the effect of zero-degree focusing is influenced strongly by th e crystal rainbow effect. (C) 2001 Elsevier Science B.V. All rights reserve d.