Positron-atom scattering using pseudo-state energy shifts

TL;DR

This paper introduces a method to calculate low-energy phase shifts for positron-atom elastic scattering using bound-state calculations and semi-empirical potentials, applied to Mg and Zn with detailed resonance and cross-section results.

Contribution

It develops a novel approach combining bound-state calculations with semi-empirical potentials to determine positron-atom scattering phase shifts and cross sections.

Findings

Identified a p-wave shape resonance in e+ - Mg at 0.096 eV.

Calculated a peak cross section of about 4800 a_0^2 for e+ - Mg.

Achieved a high Z_eff value of 1310 at 0.109 eV.

Abstract

A method to generate low-energy phase shifts for elastic scattering using bound-state calculations is applied to the problem of e+ - Mg and e+ - Zn scattering after an initial validation on the e+ - Cu system. The energy shift between a small reference calculation and the largest possible configuration interaction calculation of the lowest energy pseudo-state is used to tune a semi-empirical optical potential. The potential was further fine-tuned by utilizing the energy of the second lowest pseudo-state. The s- and p-wave phase shifts for positron scattering from Mg and Zn are given from threshold to the first excitation threshold. The e+ - Mg cross section has a prominent p-wave shape resonance at an energy of about 0.096 eV with a width of 0.106 eV. The peak cross section for e+ - Mg scattering is about 4800 a_0^2 while Z_eff achieves a value of 1310 at an energy of 0.109 eV.