Positron annihilation in perfect and imperfect metals: a brief review

The current renaissance of investigations of positron annihilation in solids has its origins in the observation that positrons interact strongly with certain crystal-lattice defects. Three properties of the annihilation process are being measured to gain information about the defects or about the local environment of the positron at the instant of its annihilation: positron lifetime, angular correlation of the two annihilation quanta, and Doppler broadening of the 511-keV annihilation line. Until the physics of positron behavior in solids is fully understood, the phenomenon will continue to be useful in a manner analogous to electrical resistivity recovery for identifying the recovery stages in irradiated metals. Ultimately, it is destined to provide detailed quantitative information such as the formation volume of vacancies, vacancy-impurity binding energies and electron momentum distributions and densities at defect sites. 2 tables, 52 refs