On the trapping of positrons by negatively charged vacancies

We have developed a simplified model for the trapping of positrons by negat ively charged vacancies. By solving the differential equations pertaining t o the population of positron states, expressions for the experimentally obs ervable positron parameters (lifetimes, their intensities and the Doppler b roadening parameter S) were obtained. We show that the temperature dependen cies of the positron parameters are markedly influenced by the ratio betwee n 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. (C) 2001 Elsevie r Science B.V. All rights reserved.