Density corrections to the positron annihilation rate in moderately dense gases

Abstract

The density and temperature dependences of the effective charge Zeff describing the free-positron annihilation rate in dense gases are investigated by means of the method of the temperature Green's functions. It is shown that the dependence is determined by correlations in positions of the atoms in the medium and by multiple scattering processes. The theoretical results are compared with the experimental data. The possibility of applying the proposed theory to the investigation of the orthopositronium annihilation rate in dense gases is discussed.