Chemical reactions of positronium studied by age-momentum correlation (AMOC) using a relativistic positron beam

Abstract

Correlated measurements of the individual positron lifetimes (so-called positron ages) and of the Doppler shift of the 2γ-annihilation photon energy (Age-Momentum Correlation, AMOC) allow the evolution of the positron states to be observed in the time domain. The AMOC technique is thus especially useful when “chemical” reactions of positronium induce transitions between positron states. The full information contained in the AMOC data may be extracted from the two-dimensional AMOC histogramme, the so-called AMOC relief, by fitting a suitable two-dimensional model function. In this way quantitative information on the spin conversion of positronium by a paramagnetic radical in the systems HTEMPO/methanol and HTEMPO/benzene and on the formation of positron bound states in aqueous solutions of various sodium halides has been deduced.