Positron motion in metals. II. Models for data analysis

Abstract

Two aspects of the momentum distribution function for positrons interacting with phonons and electrons in metals are studied. First, a simple approximation to the theoretical expression for the momentum distribution is found. It is used to clarify the meaning of the apparent mass in a Gaussian distribution introduced in the analysis of experimental data. Secondly, numerical evaluation of the theoretical momentum spectrum of the annihilating electron–positron pairs demonstrates the inadequacies of the Gaussian approximation. This leads to a new method of analysis of experimental data using the realistic distribution. This method allows one to obtain separately the positron quasiparticle mass and the positron–phonon coupling strength.