On the trapping of positrons by negatively charged vacancies

We have developed a simplified model for the trapping of positrons by negatively charged vacancies. By solving the differential equations pertaining to the population of positron states, expressions for the experimentally observable positron parameters (lifetimes, their intensities and the Doppler broadening parameter S) were obtained. We show that the temperature dependencies of the positron parameters are markedly influenced by the ratio between the trapping rate from the delocalized state to the vacancy and that from the Rydberg-like state to the vacancy. We illustrate the usefulness of the model in the case of Doppler broadening data for diamond.