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arxiv: 2606.04078 · v1 · pith:LUJATYXCnew · submitted 2026-06-02 · ⚛️ physics.chem-ph

Quantifying Electronic and Vibronic Contributions to Charge Transfer at the Nanoscale

Jessica Martinez , Eric Duverger , Michele Pavanello , Damien Riedel This is my paper

Pith reviewed 2026-06-28 07:55 UTC · model grok-4.3

classification ⚛️ physics.chem-ph
keywords charge transfervibronic contributionsMarcus-Levich-Jortner modelscanning tunneling microscopymolecular dyadsurface-supported systemstautomerizationreorganization energy
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The pith

Charge transfer rates at the nanoscale are controlled by the combined action of electronic and vibronic contributions.

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

The paper studies a non-covalent molecular dyad on a semi-insulating surface with low-temperature STM to trigger and measure charge transfer events. Tuning the energy of tunneling electrons produces periodic modulations in the observed CT rates. Fitting these rates to the Marcus-Levich-Jortner model extracts reorganization energies and identifies resonant vibronic modes that participate in the process. Extending Marcus-Antoniewicz models to explicit reaction coordinates then shows that neither electronic nor vibronic terms alone suffice; both must be treated together. The surface-supported dyad is presented as a practical platform for isolating and quantifying these contributions.

Core claim

Applying the Marcus-Levich-Jortner model to CT rates measured in an H2TPP dyad on CaF2/Si(100) reveals periodic modulation arising from resonant vibronic modes; extending the Marcus-Antoniewicz models to explicit reaction coordinates demonstrates that charge transfer is governed by the interplay between electronic and vibronic contributions.

What carries the argument

Marcus-Levich-Jortner model applied to explicit reaction coordinates in the surface-supported non-covalent dyad.

If this is right

  • CT efficiency can be tuned by matching electron energy to specific vibronic resonances.
  • Surface-supported systems supply a stable, low-temperature platform for separating electronic and vibrational reorganization energies.
  • The same rate-modulation analysis can be applied to other molecular fragments to predict CT behavior.
  • Tautomerization in one fragment serves as a readable signature of CT initiated in the other.

Where Pith is reading between the lines

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

  • Device designs that aim to control CT could deliberately engineer molecular vibrations to match desired resonances.
  • The approach may generalize to other non-covalent assemblies where direct isolation of vibronic effects has been difficult.
  • Combining STM rate measurements with DFT could become routine for mapping vibronic landscapes in nanoscale systems.

Load-bearing premise

The observed periodic modulation in CT rates arises directly from resonant vibronic modes that can be isolated by the Marcus-Levich-Jortner model without dominant interference from surface interactions or setup artifacts.

What would settle it

CT-rate measurements that show no periodic modulation with tunnel-electron energy, or extracted reorganization energies that fail to align with the vibrational frequencies computed by DFT for the same dyad.

read the original abstract

Charge transfer (CT) is governed by complex multiscale dynamics sensitive to environmental factors. In molecules, charge state and vibrational effects shape energy levels, charge distribution, and reactivity, thereby controlling CT efficiency. Quantifying these contributions in CT is experimentally challenging, as vibrational effects remain difficult to isolate due to limits in precision, sensitivity, and stability. In such context, the original Marcus theory, often lacks the refinement required to accurately capture CT rates in complex environments, necessitating new approaches that incorporate vibronic effects. Here, we examine a non-covalent H2TPP dyad on a semi-insulating CaF2/Si(100) surface. Using a low-temperature (9 K) scanning tunneling microscope (STM), we generate tunneling electrons that trigger CT events by creating locally cationic states while activating transient vibronic modes at specific molecular sites in one fragment. This initiates a meso N tautomerization serving as a CT signature in the second fragment. By tuning the tunnel electron energy, CT rates measurements reveal a periodic modulation. Quantitative analysis with the Marcus-Levich-Jortner model identifies key reorganization energies and resonant vibronic modes, while DFT provides complementary conformational and vibrational insights. Extending the Marcus-Antoniewicz models to explicit reaction coordinates reveals that CT is governed by the interplay between electronic and vibronic contributions, establishing surface-supported systems as a model framework.

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

3 major / 2 minor

Summary. The manuscript examines charge transfer (CT) in a non-covalent H2TPP dyad adsorbed on a CaF2/Si(100) surface at 9 K using low-temperature STM. Tunneling electrons are used to trigger locally cationic states and transient vibronic modes, leading to meso N tautomerization as a CT signature. Tuning the tunnel electron energy produces a periodic modulation in measured CT rates; quantitative fitting to the Marcus-Levich-Jortner (MLJ) model is used to extract reorganization energies and resonant vibronic modes. DFT supplies conformational and vibrational context. The central claim is that extending Marcus-Antoniewicz models to explicit reaction coordinates demonstrates CT is controlled by the interplay of electronic and vibronic contributions, positioning surface-supported systems as a model framework.

Significance. If the MLJ parameter extraction can be shown to be robust against surface and instrumental artifacts, the work would supply a concrete experimental route to separate electronic and vibronic contributions to CT at the nanoscale. The low-temperature STM platform and the use of tautomerization as a readable CT reporter are technically attractive features. However, the manuscript supplies no raw rate data, error bars, or fitting diagnostics, so the quantitative claims cannot yet be evaluated independently.

major comments (3)
  1. [Abstract / Quantitative analysis] Abstract and quantitative-analysis paragraph: the periodic modulation in CT rates is mapped onto resonant vibronic modes solely through MLJ fitting. No independent spectroscopic confirmation or exclusion of substrate-phonon, image-charge, or tip-field contributions is described. Because the extracted reorganization energies and mode frequencies are obtained by fitting the same model whose validity is being asserted, the attribution is circular and load-bearing for the central claim of quantified electronic-vibronic interplay.
  2. [Abstract] Abstract: the manuscript states that 'quantitative analysis with the Marcus-Levich-Jortner model identifies key reorganization energies and resonant vibronic modes' but provides neither the raw CT-rate versus energy data, the fitting procedure, nor any goodness-of-fit metrics. Without these, it is impossible to assess whether the periodicity is statistically significant or whether alternative functional forms could describe the data equally well.
  3. [Abstract] Abstract: the claim that 'surface-supported systems [are established] as a model framework' rests on the assumption that the observed periodicity arises exclusively from molecular vibronic resonances. The text does not address how the semi-insulating CaF2 layer or the Si(100) substrate phonon bath might produce or modulate the same periodicity, which directly challenges the isolation assumption required for the MLJ interpretation.
minor comments (2)
  1. [Abstract] Abstract: the phrase 'original Marcus theory, often lacks the refinement' contains a grammatical error; 'often lacks' should be rephrased for clarity.
  2. [Abstract] Abstract: the term 'meso N tautomerization' is introduced without a brief definition or reference; a short explanatory clause would aid readers unfamiliar with porphyrin tautomerism.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We address each major comment point by point below, indicating where revisions will strengthen the presentation of the quantitative analysis and supporting arguments.

read point-by-point responses

  1. Referee: [Abstract / Quantitative analysis] Abstract and quantitative-analysis paragraph: the periodic modulation in CT rates is mapped onto resonant vibronic modes solely through MLJ fitting. No independent spectroscopic confirmation or exclusion of substrate-phonon, image-charge, or tip-field contributions is described. Because the extracted reorganization energies and mode frequencies are obtained by fitting the same model whose validity is being asserted, the attribution is circular and load-bearing for the central claim of quantified electronic-vibronic interplay.

    Authors: The observed periodicity in CT rates versus tunnel electron energy is an experimental result obtained prior to any model fitting. The MLJ analysis is applied to interpret this periodicity, with the resulting mode frequencies showing direct correspondence to specific intramolecular vibrations computed by DFT. We agree that potential artifacts require explicit discussion; the revised manuscript will include a new subsection addressing why substrate-phonon, image-charge, and tip-field effects are unlikely to produce the observed energy-dependent periodicity under the stated experimental conditions (9 K, thin semi-insulating CaF2 layer). While independent spectroscopic confirmation lies outside the present STM study, the multi-technique consistency (experiment + DFT) supports the vibronic assignment. We will also report the full fitting diagnostics to allow independent evaluation. revision: partial

  2. Referee: [Abstract] Abstract: the manuscript states that 'quantitative analysis with the Marcus-Levich-Jortner model identifies key reorganization energies and resonant vibronic modes' but provides neither the raw CT-rate versus energy data, the fitting procedure, nor any goodness-of-fit metrics. Without these, it is impossible to assess whether the periodicity is statistically significant or whether alternative functional forms could describe the data equally well.

    Authors: We accept that the absence of raw data, fitting details, and goodness-of-fit metrics in the current manuscript limits independent assessment. In the revised version we will add the raw CT-rate versus energy data (as a main-text figure or SI), describe the MLJ fitting procedure explicitly, and report quantitative metrics (e.g., reduced chi-squared, R^2) together with a comparison to alternative functional forms to demonstrate that the periodic MLJ description is statistically preferred. revision: yes

  3. Referee: [Abstract] Abstract: the claim that 'surface-supported systems [are established] as a model framework' rests on the assumption that the observed periodicity arises exclusively from molecular vibronic resonances. The text does not address how the semi-insulating CaF2 layer or the Si(100) substrate phonon bath might produce or modulate the same periodicity, which directly challenges the isolation assumption required for the MLJ interpretation.

    Authors: The revised manuscript will contain an explicit paragraph discussing possible substrate contributions. The thin CaF2 decoupling layer and the 9 K temperature strongly suppress thermal phonon populations from the Si(100) bath; the observed periodicity matches the energies of intramolecular modes calculated by DFT rather than the known phonon spectrum of the substrate. These arguments will be added to justify the isolation of molecular vibronic effects. revision: yes

Circularity Check

0 steps flagged

No circularity; experimental data interpreted via established model

full rationale

The paper measures CT rates experimentally via STM, observes a periodic modulation by tuning tunnel electron energy, then applies the Marcus-Levich-Jortner model for quantitative analysis to identify reorganization energies and vibronic modes, supplemented by DFT. This constitutes standard model-based interpretation of independent experimental observations rather than any derivation in which a claimed prediction or first-principles result reduces to the input data or fitted parameters by construction. No equations, self-citations, or ansatzes are presented in the text that would create a self-definitional loop or rename a fit as a prediction. The extension of Marcus-Antoniewicz models follows from the analysis but does not collapse to the inputs.

Axiom & Free-Parameter Ledger

2 free parameters · 1 axioms · 0 invented entities

The central claim depends on the applicability of the Marcus-Levich-Jortner model to interpret rate modulations as vibronic resonances and on the assumption that DFT provides independent conformational validation. No explicit free parameters or invented entities are named in the abstract, but model fitting implies fitted reorganization energies.

free parameters (2)
  • reorganization energies
    Extracted via quantitative analysis with the Marcus-Levich-Jortner model from the measured CT rate modulation.
  • resonant vibronic modes
    Identified from the periodic modulation in CT rates using the same model.
axioms (1)
  • domain assumption Marcus-Levich-Jortner model applies directly to CT in this surface-supported molecular system.
    Invoked to identify key reorganization energies and resonant vibronic modes from the experimental rate data.

pith-pipeline@v0.9.1-grok · 5777 in / 1481 out tokens · 27588 ms · 2026-06-28T07:55:58.263620+00:00 · methodology

discussion (0)

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Reference graph

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