Convergent close-coupling approach to ion collisions with multi-electron targets: Application to $\bar{p} + {\rm C}$ collisions

TL;DR

This paper extends the convergent close-coupling method to multi-electron targets, applying it to antiproton collisions with carbon, and demonstrates the importance of a multi-core target description for accurate collision modeling.

Contribution

The authors develop a new approach using pseudostates for multi-electron targets and apply it to antiproton-carbon collisions, highlighting the necessity of multi-core models.

Findings

Multi-core target models are essential for accurate collision predictions.

The approach yields excitation energies, oscillator strengths, and cross sections consistent with experimental data.

Comparison shows multi-core models outperform frozen-core approximations.

Abstract

The single-centre convergent close-coupling approach to ion-atom collisions has been extended to model collisions involving arbitrary multi-electron atoms and partially stripped ions. This is accomplished by generating a set of target pseudostates using the configuration interaction method. The resulting pseudostates are expanded in terms of configuration state functions, constructed using a hybrid of Hartree-Fock and Coulomb-Sturmian spin-orbitals. This new approach is applied to study antiproton collisions with atomic carbon. We present excitation energies, oscillator strengths, and the dipole polarisability obtained using the target structure model to validate its accuracy. Furthermore, we present results for elastic-scattering, total excitation, and ionisation cross sections in the incident energy range between 10 to 1000 keV. State-resolved excitation cross sections for the first few dominant transitions are also presented. Throughout the manuscript, we compare results obtained using the multi-core target structure model with those from a frozen-core one. In all cases, we find that a multi-core description of the carbon atom target is essential for accurately modelling these collisions.