Positron Annihilation in Materials under Ionizing Radiation

Abstract

Positron‐annihilation lifetime spectra in tritiated water and ice are described, and the effect of irradiation products on positron‐annihilation rates in a medium is estimated. In a liquid medium the interference mainly comes from stable products accumulated during irradiation and in a solid medium from free radicals frozen in the lattice. It is also indicated that care must be taken in preparing samples for positron‐annihilation experiments to avoid excessive radiation damage to the medium by the positron source.