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Abstract
Scattering phase shifts and annihilation rates for lowenergy positrons interacting with noble gas atoms are calculated ab initio using manybody theory implemented in the Gaussianorbital code EXCITON+. Specifically, we construct the positron–atom correlation potential (selfenergy) as the sum of three classes of infinite series describing the screened polarization, virtual positronium formation, and positronhole repulsion found via the solution of Bethe–Salpeter equations for the twoparticle propagators. The normalization of the continuum states is determined using the shifted pseudostates method [A. R. Swann and G. F. Gribakin, Phys. Rev. A 101, 022702 (2020)]. Comparison with the previous sophisticated Bspline manybody approach, which is restricted to atoms [J. Ludlow, D. G. Green, and G. F. Gribakin, Phys. Rev. A 90, 032712 (2014)], validates the EXCITON+ code, which can be used for multicentered targets including molecules, clusters, and condensed matter. Moreover, the relative effects of higherorder diagrams are quantified. It is found that the screening of the electron–positron Coulomb interaction represented by the infinite ringdiagram series (randomphase approximation) is compensated effectively by the additional electronhole attraction corrections to it (the Bethe–Salpeter equation approximation) and that the use of the screened Coulomb interaction (screened at BSE level) in place of the bare Coulomb interaction in the virtual positronium and positronhole ladder diagrams has negligible effect on both the phase shifts and Z_{eff}. Our scattering length for Ne and Kr is in improved agreement with the convergent closecoupling result, and for Ar, the scattering length is in better agreement with the experiment compared with the previous Bspline manybody approach.
Original language  English 

Article number  1227652 
Number of pages  15 
Journal  Frontiers in Physics 
Volume  11 
DOIs  
Publication status  Published  28 Sept 2023 
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R6997TCP: Manybody Theory of Antimatter Interactions with Atoms, Molecules and Condensed Matter
29/10/2018 → …
Project: Research
Student theses

Manybody theory of positron interactions with molecules
Author: Hofierka, J., Jul 2024Supervisor: Green, D. (Supervisor) & Gruening, M. (Supervisor)
Student thesis: Doctoral Thesis › Doctor of Philosophy
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