Interaction of positrons and dislocations

The change in positron density due to the presence of a dislocation in a metal is calculated. The resultant change in positron lifetime is found using both the Sommerfeld independent particle model and the local screening theory of Micah and Young. The lifetime change is calculated in the case of aluminium and found to be about 1% compared with the experimentally observed change of 15%. The angular correlation function, which is a measure of the degree of positron localization, is also calculated. It is found that the experimental angular correlation can be equally well interpreted on the basis of dislocation or vacancy trapping.