Measurement method of
positron annihilation analysis in which the time interval between the emission of positrons from a radioactive source and the detection of gamma rays due to the annihilation of these positrons with electrons from the surrounding matter is the lifetime of the positron or positronium.
Source:
PAC, 2021, 93, 69. 'Vocabulary of radioanalytical methods (IUPAC Recommendations 2020)' on page 92 (https://doi.org/10.1515/pac-2019-0302)