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Path Integral Monte Carlo Simulation of Positronium within a Dielectric Spherical Cavity

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dc.contributor.advisor Bug, Amy L.
dc.contributor.author Wolfson, Zachary
dc.date.accessioned 2013-03-19T18:35:23Z
dc.date.available 2013-03-19T18:35:23Z
dc.date.issued 2006
dc.identifier.uri http://hdl.handle.net/10066/10476
dc.description.abstract Positronium (Ps), the bound state of an electron and a positron, may be used as a probe of the porous space in bulk materials due to its long vacuum lifetime and the fact that this lifetime depends strongly on its environment. In particular, an accurate model relating the lifetime of the positronium to the size of the pore is necessary. The primary outcome of this research is a computer program that models Ps exactly as two quantum particles, using Path Integral Monte Carlo (PIMC) to simulate the electron and positron each as a classical polymer. As a further correction, we include the dielectric response of the surrounding material to the presence of the two charges. We find that the material's polarization causes the Ps to be more attracted to the wall, decreasing the pickoff lifetime; this decrease is even more dramatic in the case of a bare positron within the cavity. Although this effect is more substantial for larger cavities, it does approach a limit as the radius of the cavity approaches infinity, since then the situation is that of Ps near a flat dielectric wall. Also a limit is reached in the behavior of the lifetime as the dielectric constant ko increases, since the energy scales approximately like (1- ko)/(l + ko). Using a two-particle simulation with no dielectric energy (or equivalently, setting ko = 1) in general produces lifetimes significantly higher than the standard Tao-Eldrup model, but having ko > 1 reduces the lifetime once more, agreeing with Tao-Eldrup in certain cases. We found that typical values of ko have the same order of magnitude effect as do different pore geometries, and that our results explain certain discrepancies in data that other models could not. en
dc.description.sponsorship Swarthmore College. Dept. of Physics & Astronomy en
dc.language.iso en_US en
dc.rights Full copyright to this work is retained by the student author. It may only be used for non-commercial, research, and educational purposes. All other uses are restricted.
dc.title Path Integral Monte Carlo Simulation of Positronium within a Dielectric Spherical Cavity en
dc.type Thesis (B.A.)


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