Effect of the Diffraction of Annihilation γ-Rays on Their Angular Correlation in a Single Crystal Specimen

A very sharp anisotropy of the angular correlation of annihilation radiation in a single crystal specimen was found and investigated. It proved to be attributed to the diffraction of the annihilation photons by the lattice planes of the crystal. The experiment was performed by the rotating specimen method as well as by the angular correlation method. The results showed that the diffraction of the annihilation photons makes a serious effect on the shape of the usual angular correlation curve and that the effect is very sensitive to the orientation of the crystal as expected. The integrated intensities of the diffraction peaks calculated by using the kinematical theory of X-ray diffraction were in a fairly good agreement with the experimental values.