CXLI. On the annihilation of positrons in solids

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Abstract
Using the method of delayed coincidences the lifetimes of positrons from 22Na have been determined in various materials, the 1·28 mev γ-ray of 22Na announcing the emission of a positron. A lifetime of (1·6±0·6 x 10-10 sec) has been deduced in aluminium, and comparative measurements show that it does not differ from this in other metals studied by us and by other writers. A second lifetime of (2·5±0·3 × 10-9 sec) involving (0·27±0·03) of the positrons has been found in distrene at room temperature. This lfetime has been found to increase by about 10% for 115≥c rise in temperature. Three quantum emission from distrene has been found to be small. Experiments have also been carried out in plastic sulphur and magnetized iron.