Positron-atom scattering using pseudostate energy shifts

Abstract

A method to generate low-energy phase shifts for elastic scattering using bound-state calculations is applied to the problem of ${e}^{+}\text{\ensuremath{-}}\text{Mg}$ and ${e}^{+}\text{\ensuremath{-}}\text{Zn}$ scattering after an initial validation on the ${e}^{+}\text{\ensuremath{-}}\text{Cu}$ system. The energy shift between a small reference calculation and the largest possible configuration interaction calculation of the lowest-energy pseudostate is used to tune a semiempirical optical potential. The potential was further fine-tuned by utilizing the energy of the second lowest pseudostate. The $s$- and $p$-wave phase shifts for positron scattering from Mg and Zn are given from threshold to the first excitation threshold. The ${e}^{+}\text{\ensuremath{-}}\text{Mg}$ 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 ${e}^{+}\text{\ensuremath{-}}\text{Mg}$ scattering is about $4800{a}_{0}^{2}$, while ${Z}_{\text{eff}}$ achieves a value of 1310 at an energy of 0.109 eV.