Electric field dependence of positronium formation in condensed matter

Electrostatic fields affect the lifetime spectra of positrons annihilating in normal paraffins and polyethylenes. The intensity of the longest lived of the three resolved lifetime components decreases by almost 50% at the highest fields ({~}200 kV/cm). The dependences of the data on density, temperature, and electric field are interlinked in a comprehensive manner by a theory which depends parametrically on the cross sections for the interaction of epithermal positrons with the molecular (-CH₂-) repeat units. Inferences are drawn for electronic subionization processes in insulators.