Theory of Positron Annihilation in Inert-Gas Solids

Abstract

We have calculated the lifetime of a positron in solid argon as a function of two-quantum decay and the angular correlation of the resulting $\gamma$ pair. The shape of the angular distribution obtained is in close agreement with experiment, and the area under it gives the measured total rate to within 15%. The calculations are based on a general theory that was developed for annihilation in metals but is also applicable with slight modifications to simple nonionic insulators like the inert-gas solids where a single decay mode is observed. The point is simply that we can treat all electrons as core electrons, and the expressions previously derived for core annihilation in metals can readily be adapted to simple nonionic insulators.