A Monte Carlo simulation of the effect of the surface oxide layer on blocking dips

A BCA Monte Carlo method which takes into account the surface amorphous layer was used to calculate the blocking dips around <110> axis in Al single crystal of α-particles of about 2 MeV, produced at a depth of 0.2μm. The thermal vibrations of the lattice atoms and the electronic multiple scattering are taken into account. The resulting blocking dips were compared with the measurements relative to the 'zero reaction time' (p,α) resonance at 1183 keV in Al crystals. By properly taking into account the amorphous surface layer an angular distribution of emerging α-particles from the crystals was obtained that agrees well with the experimental one. (author)