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Published on: April 8, 2020
Pick-off annihilation of positronium in matter using full correlation single particle potentials: solid He.
A Zubiaga1, F Tuomisto, M J Puska
1Department of Applied Physics, Aalto University , P.O. Box 14100, FIN-00076 Aalto Espoo, Finland.
We developed a new model for positronium (Ps) annihilation in molecular matter. This model accurately predicts annihilation rates and void sizes, improving upon existing methods like the Tao-Eldrup model.
Area of Science:
- Atomic and Molecular Physics
- Condensed Matter Physics
- Materials Science
Background:
- Positronium (Ps) annihilation is a sensitive probe of open-volume defects in condensed matter.
- Existing models like the Tao-Eldrup model have limitations in accurately describing Ps interactions within complex molecular environments.
- Understanding Ps behavior in voids is crucial for materials characterization and defect analysis.
Purpose of the Study:
- To develop and validate a theoretical model for positronium annihilation in open-volume defects within condensed molecular matter.
- To accurately calculate Ps states and pick-off annihilation rates in voids.
- To assess the validity of the widely used Tao-Eldrup model against theoretical predictions.
Main Methods:
- Utilized an interacting many-body system of Ps and a Helium (He) atom as a foundational model.
- Employed exact-diagonalization to solve the HePs system and construct a pairwise potential.
- Superposed pairwise potentials to model the total interaction potential in solids.
- Analyzed experimental data for Ps-induced voids in liquid He.
Main Results:
- Developed a pairwise full-correlation single-particle potential for Ps-He interactions.
- Accurately modeled Ps states and pick-off annihilation rates in voids within solid He.
- Validated theoretical predictions against experimental results for void radii in liquid He.
- Demonstrated limitations of the Tao-Eldrup model for certain condensed matter systems.
Conclusions:
- The developed theoretical framework provides a more accurate description of positronium annihilation in open volumes.
- The study offers insights into the influence of molecular properties (partial charges, van der Waals interactions) on annihilation rates.
- This work refines the understanding of positronium annihilation spectroscopy for materials defect analysis.
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