Modified master equation approach of axial dechanneling in perfect compound crystals

The master equation approach of dechanneling based on the channeling concept of Lindhard underestimates the Rutherford backscattering minimum yield of perfect crystals mainly at small depths where the equilibrium in the transverse energy shell is not yet reached. This paper presents a modification of the master equation approach which overcomes this problem. The main idea is to simulate the minimum yield up to a depth Z(equi) where the equilibrium is reached and modify the initial distribution of the ions in the master equation approach in this way that the calculated minimum yield at that depth Z(equi) is equal to the corresponding simulated one. Because the simulated depth interval is small, the numerical calculation is still fast enough to be applied for the evaluation of Rutherford backscattering data. For some examples of perfect crystals the results of the calculated minimum yields are compared with those obtained by full simulations and in two cases also with experimental data. (C) 2004 Elsevier B.V. All rights reserved.