Comments on the Diffraction Effect in Positron Annihilation

Abstract

Several comments are given on the diffraction effect of annihilation gamma rays in a single crystal (cf. Hyodo et al.: J. Phys. Soc. Japan 31 (1971) 563). It is shown that the feature of this effect on the angular-correlation curve depends on the type of the apparatus. It is proved to be impossible to measure the momentum distribution of electron pairs along the direction strictly (within the error of less than a few milliradians) perpendicular to the lattice plane. The integrated intensity of the diffraction in copper has been remeasured with a better statistics. It agrees with the theoretical value within the experimental error of 5%.