Enhancement Effect on Positron Annihilation with Tightly Bound Electrons

Coulomb correlation is taken into account in the annihilation process of positrons in solids with tightly bound electrons by first‐order perturbation theory. A momentum‐dependent enhancement formula is derived which is applicable to insulators with high electron density. With the use of the Thomas‐Fermi approximation the formula is reduced to give an annihilation rate depending solely on the overlap density of electrons and a positron. It is shown that the annihilation rates in insulators follow an enhancement curve different from that for metals.