Electron paramagnetic resonance and optical studies were made of vacancies and interstitials produced in type-IIa diamond irradiated with 2MeV electrons at between 90 and 900K. Post-irradiation annealing studies at up to 1900K were also performed. Data showing recombination-enhanced diffusion of self-interstitial atoms in diamond were presented and analysis of the phenomena led to the conclusion that a highly mobile interstitial 1* (possibly a charged/neutral Td interstitial) was produced by electronic excitation and/or charge transfer. It was estimated that the migration energy for 1* was 0.3eV. No evidence of vacancy recombination-enhanced diffusion was observed. The experimental data confirmed that there was a significant barrier to vacancy-interstitial recombination in diamond. Recombination-Enhanced Diffusion of Self-Interstitial Atoms and Vacancy-Interstitial Recombination in Diamond. Newton, M.E., Campbell, B.A., Twitchen, D.J., Baker, J.M., Anthony, T.R.: Diamond and Related Materials, 2002, 11[3-6], 618-22