The temperature dependence of the coincidence counting rates of two annihilation photons was measured. Analysing the results using the trapping model, the formation energy of a vacancy in Cu was determined to be 1.17eV.

The Measurement of the Formation Energy of a Vacancy in Cu by Positron Annihilation. S.Nanao, K.Kuribayashi, S.Tanigawa, M.Mori, M.Doyama: Journal of Physics F, 1973, 3[1], L5-8