Two-dimensional analysis of positron age-momentum correlation (AMOC) data

By measuring the individual positron lifetimes (= positron ages) together with the energies of one of the annihilation quanta in a triple-coincidence set-up (age-momentum correlation, AMOC), time-resolved information on the evolution of the positron states may be obtained. The present paper describes a data evaluation procedure that makes full use of the time-resolved information provided by the AMOC relief (number of counts versus positron age and photon energy) by fitting the parameters of an appropriate physical model directly to the two-dimensional relief without prior data reduction. The power of this novel analysis is illustrated by analyzing complex formation and spin conversion of positronium in solutions of HTEMPO in solid and liquid benzene.