Thermal smearing of positron angular correlation in solid and liquid metals

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Abstract
The positron partial annihilation rates near the Fermi surface in the alkali solid and liquid metals are calculated by using second order perturbation theory for the temperature dependent Green function, including the ionic density correlation. In both cases, solid and liquid, the contributions from the Coulomb interactions to the enhancement factors are assumed to be constant. An Ashcroft pseudopotential is used for the electron-ion interaction, while a selfconsistent potential model is used for the positron-ion interaction within the framework of the pseudopotential model. The calculated annihilation rates are compared with the experimental data for Na and Rb through the counting rate curve.