Positron annihilation and vacancy formation in Al

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Abstract
High-precision measurements of the temperature dependence of positron annihilation in Al, over the range 290-930K, have been made via the Doppler-broadening technique and using an internal 68Ge positron source. The results are considered mainly in terms of two lineshape parameters. These are denoted L and W and describe, respectively, the intensities of well defined central and wing portions of a normalised annihilation photopeak area. Both L and W exhibit the characteristic, overall S-shaped temperature-dependence profile associated with the change from free to vacancy-trapped annihilation modes. In detail, however, the temperature dependences of L and W are quite distinct.