Gaussian-basis many-body theory calculations of positron binding to negative ions and atoms

• URL: http://arxiv.org/abs/2311.13066v1
• Date: Tue, 21 Nov 2023 23:55:47 GMT
• Title: Gaussian-basis many-body theory calculations of positron binding to negative ions and atoms
• Authors: J. Hofierka, B. Cunningham, C. M. Rawlins, C. H. Patterson and D. G. Green
• Abstract summary: The binding energies in the negative ions H$-$, F$-$, Cl$-$ and Brtron-$ are calculated via a many-body theory approach. For the atoms, for which binding is enabled exclusively by correlations, the binding energies are found to be $sim$10-30% larger than relativistic coupled-cluster calculations.
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• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Positron binding energies in the negative ions H$^-$, F$^-$, Cl$^-$ and Br$^-$, and the closed-shell atoms Be, Mg, Zn and Ca, are calculated via a many-body theory approach developed by the authors [J.~Hofierka \emph{et al.} Nature~{\bf 608}, 688-693 (2022)]. Specifically, the Dyson equation is solved using a Gaussian basis, with the positron self energy constructed from three infinite classes of diagrams that account for the strong positron-atom correlations that characterise the system including the positron-induced polarization of the electron cloud, screening of the electron-positron Coulomb interaction, virtual-positronium formation and electron-hole and positron-hole interactions. For the negative ions, binding occurs at the static level of theory, and the correlations are found to enhance the binding energies by $\sim$25--50\%, yielding results in good agreement with ($\lesssim$5\% larger than) calculations from a number of distinct methods. For the atoms, for which binding is enabled exclusively by correlations, most notably virtual-Ps formation, the binding energies are found to be of similar order to (but $\sim$10--30\% larger than) relativistic coupled-cluster calculations of [C. Harabati, V.~A.~Dzuba and V.~V. Flambaum, Phys.~Rev.~A {\bf 89}, 022517 (2014)], both of which are systematically larger than stochastic variational calculations of [M.~Bromley and J.~Mitroy, Phys.~Rev.~A {\bf 73} (2005); J.~Mitroy, J.~At.~Mol.~Sci.~{\bf 1}, 275 (2010)].

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