The effect of lattice thermal vibrations on particle dechannelling

The experimental values of the integral dechannelling function of protons with 1MeV intitial energy are presented. The values have been obtained for the four most open channels of W crystal and six channels of Ge crystal. The dechannelling mechanism due to crystal atom thermal vibrations is discussed. Account is taken that not only the particle momentum fluctuations but also the fluctuations of particle position in the transverse plane after a scattering event give rise to the changes of the transverse energy when the particle is scattered by a displaced chain atom. The correlations of thermal displacements of crystal atoms have been included by examining the result of scattering by an individual atomic string. The integral dechannelling function is calculated. The contribution from multiple scattering by electrons to the dechannelling is discussed on the basis of the methods developed earlier to calculate the channelled particle energy loss. The comparison with experimental data has shown that the inclusion of the correlations of the crystal thermal vibrations can significantly improve the agreement with experiment. The results obtained may be treated to be a substantiation for the possibility of deriving fresh information about lattice vibrations from the experimental data on the dechannelling. (author)