Comments on the relation: positronium lifetime – free volume size parameters of the Tao–Eldrup model

The author is discussing the parameters appearing in the Tao–Eldrup (TE) model describing the ortho-positronium (o-Ps) lifetime dependence on the size of free volume in which Ps is trapped. Parameter values are not universal, applicable to all media. The Ps penetration to the bulk should depend on Ps work function; the o-Ps decay rate is strongly influenced by the contact density factor.