Effect of dipole polarizability on positron binding by strongly polar molecules

TL;DR

This paper develops a model for positron binding to polar molecules that incorporates dipole and polarization effects, improving prediction accuracy and physical consistency over simpler models.

Contribution

It introduces a combined perturbative and non-perturbative polarization model to better predict positron binding energies and core radii in polar molecules.

Findings

Perturbative model reliably predicts binding energies for various molecules.

Non-perturbative polarization treatment yields physically meaningful core radii.

Model agrees with experimental linear dependence of binding energies on polarizability.

Abstract

A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to unphysically small core radii for all of the molecules studied. This suggests that electron-positron correlations neglected in the simple model play a large role in determining the binding energy. We account for these by including polarization potential via perturbation theory and non-perturbatively. The perturbative model makes reliable predictions of binding energies for a range of polar organic molecules and hydrogen cyanide. The model also agrees with the linear dependence of the binding energies on the polarizability inferred from the experimental data [Danielson et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 235203]. The effective core radii, however, remain unphysically small for most molecules. Treating molecular polarization non-perturbatively leads to physically meaningful core radii for all of the molecules studied and enables even more accurate predictions of binding energies to be made for nearly all of the molecules considered.