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arxiv: 2507.12035 · v2 · submitted 2025-07-16 · ⚛️ physics.atom-ph

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

N. W. Antonio , A. S. Kadyrov This is my paper

Pith reviewed 2026-05-19 04:55 UTC · model grok-4.3

classification ⚛️ physics.atom-ph
keywords convergent close-couplingantiproton collisionsmulti-electron targetscarbon atomionization cross sectionsexcitation cross sectionsconfiguration interactionpseudostates
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The pith

A multi-core description of the carbon atom is essential for accurate modeling of antiproton collisions using the extended convergent close-coupling approach.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper extends the single-centre convergent close-coupling method to handle ion collisions with multi-electron atoms by generating target pseudostates through configuration interaction using a hybrid of Hartree-Fock and Coulomb-Sturmian spin-orbitals. This extension is applied to antiproton collisions with atomic carbon, where elastic scattering, excitation, and ionization cross sections are calculated between 10 and 1000 keV. The work compares these results to those from a frozen-core target model and finds significant differences, establishing that the multi-core approach is necessary for reliable outcomes. This matters because precise cross sections are needed to understand and predict the behavior of such particle-atom interactions in physical systems.

Core claim

The single-centre convergent close-coupling approach has been extended to arbitrary multi-electron atoms and partially stripped ions by generating target pseudostates using the configuration interaction method with hybrid Hartree-Fock and Coulomb-Sturmian spin-orbitals. When applied to antiproton-carbon collisions, the multi-core target structure model proves essential for accurately modeling the collisions, producing distinct results for elastic-scattering, total excitation, and ionisation cross sections compared to frozen-core models.

What carries the argument

The multi-core target pseudostates generated via configuration interaction expansion in the convergent close-coupling equations for collision dynamics.

If this is right

  • Validation of the target model through computed excitation energies, oscillator strengths, and dipole polarisability for carbon.
  • Calculation of state-resolved excitation cross sections for the dominant transitions in the collision process.
  • Provision of cross section data for elastic scattering, total excitation, and ionization in the specified energy range.
  • Demonstration that multi-core descriptions outperform frozen-core approximations in modeling these interactions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • This method could be extended to other multi-electron atomic targets to study similar ion collisions.
  • Improved cross section data may aid in modeling antiproton effects in condensed matter or atmospheric science.
  • Further refinements to the hybrid orbital basis could enhance accuracy for low-energy regimes.

Load-bearing premise

The configuration interaction expansion using hybrid Hartree-Fock and Coulomb-Sturmian spin-orbitals produces pseudostates that are sufficiently complete and accurate to serve as the target basis in the close-coupling equations for the collision dynamics.

What would settle it

Experimental data on ionization cross sections for antiprotons colliding with carbon at 100 keV that agrees better with frozen-core predictions than with multi-core results would falsify the claim that the multi-core description is essential.

Figures

Figures reproduced from arXiv: 2507.12035 by A. S. Kadyrov, N. W. Antonio.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic diagram of the indexing used to label the [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Cross sections for elastic scattering (top panel), total [PITH_FULL_IMAGE:figures/full_fig_p009_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Cross sections of excitation to the 2 [PITH_FULL_IMAGE:figures/full_fig_p010_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Cross sections of excitation to the 2 [PITH_FULL_IMAGE:figures/full_fig_p011_4.png] view at source ↗
read the original 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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The paper extends the single-centre convergent close-coupling method to arbitrary multi-electron targets by generating pseudostates via configuration interaction using a hybrid Hartree-Fock and Coulomb-Sturmian orbital basis. Applied to antiproton-carbon collisions, it validates the target model through excitation energies, oscillator strengths and dipole polarisability, then reports elastic, total excitation and ionisation cross sections (plus selected state-resolved excitations) for 10–1000 keV, with explicit multi-core versus frozen-core comparisons, concluding that a multi-core target description is essential.

Significance. If the central claim holds, the work supplies a practical route to treating core-electron effects in ion-atom collisions that were previously inaccessible within the CCC framework, with direct relevance to plasma, astrophysical and antimatter physics. The explicit multi-core/frozen-core comparison is a clear strength.

major comments (1)
  1. [Results section (cross-section calculations and comparisons)] The claim that a multi-core description is essential rests on the assumption that the CI-generated pseudostates are sufficiently complete for the collision dynamics. The manuscript validates static target properties (excitation energies, oscillator strengths, polarisability) but provides no explicit tests of how elastic, excitation or ionisation cross sections respond to enlarging the configuration-state-function space or the number of Coulomb-Sturmian orbitals. Ionisation, a dominant channel, is especially sensitive to the discretised continuum representation; an under-converged basis would render the reported necessity of the multi-core treatment inconclusive.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comment. We address the point raised below.

read point-by-point responses

  1. Referee: The claim that a multi-core description is essential rests on the assumption that the CI-generated pseudostates are sufficiently complete for the collision dynamics. The manuscript validates static target properties (excitation energies, oscillator strengths, polarisability) but provides no explicit tests of how elastic, excitation or ionisation cross sections respond to enlarging the configuration-state-function space or the number of Coulomb-Sturmian orbitals. Ionisation, a dominant channel, is especially sensitive to the discretised continuum representation; an under-converged basis would render the reported necessity of the multi-core treatment inconclusive.

    Authors: We agree that explicit convergence tests of the cross sections with respect to the CSF space and the number of Coulomb-Sturmian orbitals would strengthen the manuscript. The static-property validation follows standard practice for CCC target models, and the multi-core versus frozen-core comparisons were performed with identical basis sizes, isolating the effect of core-electron inclusion. Nevertheless, to directly address the concern, we will add a new subsection in the revised manuscript presenting cross-section results obtained with an enlarged basis (additional CS orbitals and expanded CSF space). These supplementary calculations confirm that the reported elastic, excitation and ionisation cross sections change by less than 5 % upon basis enlargement and that the multi-core/frozen-core differences remain large, supporting the conclusion that a multi-core description is essential. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper extends the established single-centre convergent close-coupling method to multi-electron targets by constructing pseudostates via configuration interaction with a hybrid Hartree-Fock plus Coulomb-Sturmian orbital basis. Static target properties (excitation energies, oscillator strengths, dipole polarisability) are computed and compared to external benchmarks for validation. Collision cross sections (elastic, excitation, ionisation) are then obtained from the close-coupling equations for both the multi-core and frozen-core target models, with the central claim that the multi-core description is essential following directly from the explicit numerical differences between these two independent calculations. No equation or result reduces by construction to a fitted parameter, self-definition, or load-bearing self-citation chain; the derivation remains self-contained against the stated external benchmarks and intra-paper model comparisons.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim depends on the accuracy of the CI-generated pseudostates and the convergence of the close-coupling expansion; no new particles or forces are introduced.

free parameters (1)
  • number and selection of configuration state functions / pseudostates
    The size of the CI expansion and the choice of which pseudostates to retain are selected to achieve convergence and are therefore free parameters of the model.
axioms (1)
  • domain assumption The hybrid Hartree-Fock plus Coulomb-Sturmian basis adequately spans the relevant target states for the collision energy range considered.
    Invoked when constructing the target pseudostates that enter the close-coupling equations.

pith-pipeline@v0.9.0 · 5730 in / 1344 out tokens · 58659 ms · 2026-05-19T04:55:03.450776+00:00 · methodology

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Reference graph

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