Origin of the low lifetimes for the localized o-PS in the large pores of porous materials: A new finding by the combination model of quantum and semi-classical physics

Positron annihilation is of great interest for applications in evaluating material structures in range from a few angstroms to hundreds of nanometers. Here, we report on a new model for calculating the free volume size in porous materials from the experimental ortho-Positronium (o-Ps) lifetimes reported and updated over than past four decades by the combination of the quantum and semi-classical physics models.