The positronium atom (Ps) is widely used as a probe to characterize nanoporous and mesoporous materials. Existing theoretical models for describing Ps annihilation rates by pick-off processes generally treat Ps as a point particle confined in a potential well. Hence these models do not justify any change in the internal structure of Ps, which is experimentally accessible by means of the contact density parameter. Recently we formulated a two-particle model in which only the electron is confined in the cavity, while the positron is moving freely and feels the medium via a positive work function. We present here a numerical treatment of the problem of calculating contact densities and pick-off annihilation rates, by using a variational method. Results are in agreement with experimental data for a large class of materials, and suggest a way to connect these data with pore sizes and positron work functions.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.