Localization of Positronium in Polymers
A good correlation is found between ortho-positronium (o-Ps) pick-off annihilation lifetimes and surface tensions of molecular liquids and polymers. Systematic shortening of the o-Ps lifetime with increasing surface tension suggests that the hole for Ps localization in polymers may be that subjected to considerable expansion as in liquids. The driving force of this hole expansion is the large quantum mechanical zero-point energy of a light particle confined in an angstrom size space. The hole expansion is insignificant in a larger nm scale pore, where the zero-point energy is much lowered.
Y. Kobayashi and T. Ichikawa, "Localization of Positronium in Polymers", Materials Science Forum, Vol. 666, pp. 67-70, 2011