Single-quantum annihilation of positrons with K -shell electrons

Reevaluations of the total K-shell cross sections of single-quantum annihilation of positrons have been made by taking into account the L-shell contribution. Z dependence of the cross section was studied for five high-Z elements, Z=50, 73, 79, 82, and 92, and for 300-keV positrons. Energy dependence has also been investigated for the last two elements in the energy region of 250-400 keV. Comparisons with theoretical predictions including the screening effect are also made.