Positronium Formation as a Probe of Polymer Surfaces and Thin Films

This is the authors' abstract. We don't add key points for this paper.

The lifetime, τ₃, and formation fraction, I₃, of triplet positronium decaying in the void volume near a polymer surface are measured versus the positron implantation energy, E. The strong E dependence of I₃ supports a spur-electron capture model of Ps formation with deduced spur sizes ranging from 200 to 660 {}. Thin film measurements indicate that the mean probe depth can be much smaller, given mainly by the average positron implantation distance, z̄(E). Surface-induced changes in the void size and glass transition temperature of polystyrene are searched for at z̄≈40.