Single-quantum annihilation of positrons at low energies

TL;DR

This paper analyzes low-energy positron annihilation with bound electrons, deriving analytical expressions for cross sections considering Coulomb and screened potentials, highlighting the universal impact of screening on annihilation probabilities.

Contribution

It provides new analytical formulas for positron annihilation cross sections near threshold, demonstrating the universal effects of screening regardless of atomic potential details.

Findings

Screening significantly increases the annihilation cross section.

Derived simple analytical expressions for Coulomb and screened potentials.

Results are universal, independent of atomic potential specifics.

Abstract

We discuss the single-quantum positron annihilation with a bound electron in the near threshold region. The angular distribution and the total cross section are considered. We obtain a simple analytical expression for the Coulomb potential and for the screened potential. It is worth noting that the obtained results for the screened potential are universal and independent of the explicit form of the atomic potential. It is shown that screening significantly increases the cross section. We also obtain the analogous results for bound-free $e^+e^-$ photoproduction.