On the temperature dependence of the positron annihilation spectrum from a single crystal of zinc

Abstract
The Doppler-broadened positron annihilation spectrum from a single crystal of zinc has been studied as a function of temperature and of the direction of photon emission. An anisotropy in the behaviour of the spectrum line height parameter was observed in the prevacancy temperature region with linear slopes 0.60*10-4K-1 in the (0001) direction and 1.02*10-4K-1 for (1010). Optimum fittings with the two-state trapping model gave differing values for the monovacancy formation enthalpy, implying an inadequacy in the present understanding of the prevacancy rise.