Many-body theory calculations of positron binding to parabenzoquinone

TL;DR

This study uses advanced many-body theory to calculate positron binding energies and annihilation rates in parabenzoquinone, revealing the influence of molecular structure and electron correlations on positron interactions.

Contribution

It provides the first detailed ab initio calculations of positron binding to parabenzoquinone, highlighting the effects of electron correlations and molecular features on positron binding energies.

Findings

Positron binding energy in parabenzoquinone is 60±16 meV.

Positron contact density in parabenzoquinone is 8.0×10⁻³ a.u.

Binding energy is significantly larger than recent scattering estimates but smaller than in benzene.

Abstract

Positron binding in parabenzoquinone is studied using \textit{ab initio} many-body theory. The effects of electron-positron correlations including polarization, virtual positronium formation and positron-hole repulsion, as well as those of $\pi$ bonds, aromaticity, and lone electron pairs, are considered. The binding energy is calculated as 60$\pm$16 meV, considerably larger than the 0.0925 meV value inferred from recent scattering calculations of [G. Moreira and M. Bettega, {\emph{Eur.~Phys.~J.~D}} {\bf 78} (2024)], but substantially smaller than we find in benzene (148$\pm$26 meV). The positron contact density (lifetime) is calculated as 8.0$\times10^{-3}$ a.u. (2.48 ns), vs.~1.61$\times 10^{-2}$ a.u. (0.81 ns) in benzene. The decrease (increase) in binding (annihilation rate) in parabenzoquinone compared to benzene is ascribed to the loss of aromaticity: the electron density on the positive oxygen nuclei being relatively harder for the positron to probe compared to the aromatic rings in benzene.