Channeling in single crystals with disordered surface layers

Channeling measurements by backscattering technique have been made on single crystals of CaF2 covered with different disordered surface layers. The minimum yield, the critical angle, and the depth dependence of the aligned yield were measured as a function of surface conditions. By comparing the experimentally found minimum yields with values obtained from calculated angular distributions based on plural scattering theory an indication of the magnitude of the scattering created by the different disordered layers has been obtained.