An Examination of the Angular Correlation of Annihilation Radiation in Silicon Single Crystal

The angular correlation of annihilation radiation along the [110]-axis in silicon has been measured at 120∼130 K with a special care in orienting the crystal. As predicted by a recent many-body theory of the annihilation of free positrons in a simplest nearly-free-electron system (K. Fujiwara, T. Hyodo and J. Ohyama: J. Phys. Soc. Japan 33 (1972) 1047), the cut-off of the narrow component at the angle corresponding to the filled zone face has been found to be sharper than that given by the independent-particle computation of Stroud and Ehrenreich.