The momentum distribution of annihilating positron-electron pairs in aluminum

Experimental and theoretical results for the momentum distribution of the positron-electron pairs in defect-free bulk Al and Al containing vacancies are presented. The experimental data was obtained using a two-Ge-detector coincidence measurement of the Doppler broadening of the annihilation radiation. This setup enables an accurate measurement of the high-momentum part of the spectrum, thereby making it possible to compare experimental and theoretical results over a wider momentum range. Various approximations of the localized positron wave function (in the presence of an ideal monovacancy) are discussed.