An experimental test on the distribution of positronium lifetimes in polymers

Positron lifetime spectra in poly[1-(trimethylsilyl)propine] membranes were collected at different temperatures and various number of accumulated counts, to compare different positronium decay models. Analysis into four discrete components shows a systematic worsening of the chi(2) test at increasing statistics. On the other hand, deconvolutions obtained using five discrete components display very good chi(2) and support the existence of a distribution of lifetimes: indeed, comparable chi(2) were obtained from an analysis which allows the longest lifetime component to be distributed. A set of simulated spectra, analysed according to the same procedure followed for the experimental data, confirmed the results obtained from the measurements. (C) 1998 Elsevier Science B.V. All rights reserved.