REVIEW 2 major objections 4 minor 40 references
Reply to Comment on "Revisiting the divergent multipole expansion of atom-surface interactions: Hydrogen and positronium, alpha-quartz, and physisorption" (arXiv:2501.14803)
T0 review · 2 major / 4 minor · reviewed 2026-08-09 · deepseek-v4-flash
Pith's one-line read The Reply argues that the Comment's criticism is misplaced: the short-range atom-surface expansion is limited by $z\ll\chi a_0/\alpha$, not $z\ll\lambda_0$, and the reference-plane shift justifies extending Lifshitz theory into the…
desk verdict A competent Reply that re-derives the standard reference-plane formalism, but its central rebuttal of the Comment's range condition rests on the author's own prior numerical work rather than on new evidence. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The mechanism is the reference-plane correction: one replaces the Lifshitz factor $1/z^3$ with $1/(z-z_0)^3$, where $z_0$ is a frequency-weighted centroid of the solid's induced charge obtained from the nonlocal response function. The second ingredient is the short-range cutoff condition $z\ll\chi a_0/\alpha$, with $\chi=\sqrt{\alpha_{\mathrm{a.u.}}(0)/Z}$ taken from the author's earlier work, which sets where retardation invalidates the nonretarded expansion.
What would settle it
Compute the exact nonretarded-plus-retarded interaction energy for hydrogen and positronium on $\alpha$-quartz at separations from 5 to 50 atomic units using a nonlocal response function for the solid; if the reference-plane expression $1/(z-z_0)^3$ plus quadrupole corrections deviates from the full result before the claimed short-range cutoff, the Reply's defense fails.
Extended reading notes
Core claim
The central claim is that the Comment's criticism rests on a misunderstanding of both the short-range cutoff and the extension to close approach. For the short range, the Reply maintains that the condition $z\ll\lambda_0$ (with $\lambda_0$ an absorption wavelength) overestimates where the nonretarded expansion applies; the correct condition is $z\ll\chi a_0/\alpha$, verified numerically in the author's prior work, so for hydrogen the breakdown occurs near $z\approx 201a_0$. For close approach, the Reply recalls the reference-plane formalism in which the atom-surface separation is measured from a plane $z_0$ characterizing the induced-charge centroid of the solid, and maintains that this makes the extension of Lifshitz theory down to $z\sim d$ (physisorption distances of a few atomic units) a well-established procedure. On that basis the Reply asserts that the original paper's physisorption analysis, including a 15 meV quadrupole correction for Kr on Cu(111), is sound.
Load-bearing premise
The Reply's case collapses if either premise fails: that the short-range atom-wall formula really is valid up to the distance $z\ll\chi a_0/\alpha$ rather than up to the much larger absorption wavelength, and that the reference-plane replacement $1/z^3\to 1/(z-z_0)^3$ stays accurate at physisorption separations.
Editorial extensions
If this is right
- If the Reply is correct, the nonretarded $1/z^3$ regime for hydrogen ends near $z\approx 201a_0$, far below the absorption-wavelength bound, so retardation enters earlier than the Comment assumes.
- The quadrupole correction is a genuine 14.2% effect in the Kr/Cu(111) physisorption energy (15 meV added to the 106 meV dipole-plus-contact contribution), so multipole terms beyond the dipole matter in physisorption.
- The coordinate $z$ in the original atom-surface formulas must be interpreted relative to the reference plane $z_0$, which is of order the Bohr radius for the systems considered, rather than relative to the geometric surface.
- At zero temperature the long-range $1/z^4$ regime extends to arbitrarily large separations; the finite-temperature $1/z^3$ tail is a separate effect that vanishes as $T\to 0$.
Reading between the lines
- Editorial inference: the cutoff condition $z\ll\chi a_0/\alpha$ ties the short-range limit to static polarizability and electron number, so species with different $\chi$ should show noticeably different onset distances for retardation; a full dynamical calculation for one such species could test this.
- Editorial inference: if the reference-plane shift is taken literally, every multipole term in the atom-surface expansion depends on $z-z_0$, so fits that ignore $z_0$ may quietly absorb it into effective parameters.
- Editorial inference: a nonlocal, atomistically resolved calculation of the response of $\alpha$-quartz at separations of 5–50 atomic units would settle the disputed physisorption range independently of the range-condition debate.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This Reply responds to Klimchitskaya's Comment on Jentschura's earlier paper concerning the multipole expansion of atom-surface interactions. The Reply makes three main points: (i) the short-range expansion of the atom-surface interaction is valid up to z << χ a0/α, with χ = sqrt(α_a.u.(0)/Z), and the Comment's upper bound λ0 is too large; (ii) the long-range 1/z^4 expressions in the original paper are correct in the context of zero-temperature field theory, while the Comment's finite-temperature bounds apply only after a modification; and (iii) the application of the theory at physisorption distances is justified by the Zaremba-Kohn reference-plane extension of Lifshitz theory, and the quadrupole correction is phenomenologically relevant. The Reply recalls a derivation of the reference-plane correction from the nonlocal response function of the solid and argues that the Comment fails to appreciate results presented in the author's Ref. [4].
Significance. If correct, the Reply would validate the range conditions and physisorption applications of the original paper against the Comment's objections. The Reply usefully clarifies the distinction between zero-temperature and finite-temperature field theory for the long-range regime, and its derivation of the reference-plane correction is a clear restatement of an established formalism. The main significance depends on whether the numerical support provided in Ref. [4] is accepted, since the Reply itself does not reproduce the key derivation or the breakdown distances. The Reply also contains a potentially important admission that the original paper's z-coordinate in the α-quartz examples should have been measured from a reference plane that was not calculated there, which leaves a quantitative gap in the defense.
major comments (2)
- [Considerations within Lifshitz theory, Eq. (3)] The central refutation of the Comment's upper-limit criticism rests entirely on Eq. (3), z << χ a0/α, and on the quoted breakdown distances (201 a0 for hydrogen and 1300 a0 for metastable helium on gold), all taken from Ref. [4]. The Reply states 'We have performed extensive numerical calculations to support the condition (3), as detailed in Ref. [4]' but does not reproduce the calculation, the numerical criterion, or the physical argument that the static polarizability ratio χ determines the onset of retardation. As a Reply, this is a load-bearing point: without seeing the derivation or at least a concise explanation of why the static ratio governs the crossover, the Reply does not by itself demonstrate that the Comment's range criticism misfires. I request that the Reply include a sketch of the derivation or a table of the calculated breakdown distances, or otherwise make the case self-contained.
- [Considerations beyond Lifshitz theory and Conclusions] In the final substantive paragraph, the Reply states that 'The z coordinate in Eqs. (62) and (63) of our paper [3] should be interpreted in terms of the distance of the z-coordinate of the hydrogen and positronium atoms with respect to the reference plane z0, whose calculation has not been considered in Ref. [3] for the respective systems at hand.' Since the Reply earlier states that z0 is of the order of a0 and the original results are quoted at z=10 a.u., this admission implies that the effective distance is changed by an amount comparable to a0, potentially altering the numerical conclusions of Ref. [3]. The Reply does not quantify this shift or state whether the original numbers require revision. This is directly relevant to the Comment's challenge to the physisorption application, and the Reply should either compute z0 for hydrogen and positronium on α-quartz or explicitly acknowledge the resulting uncertainty in the original paper's predictions.
minor comments (4)
- [General Remarks] On page 1, 'estimates for the transition region to the retarded regime have 5een indicated' contains a typo: '5een' should read 'been'.
- [References] Reference [19] gives the page range as '3541–3350' and Reference [16] contains 'Phenomane' in the title; these appear to be typographical errors ('3541–3550' and 'Phenomena' respectively).
- [Considerations within Lifshitz theory, Eq. (2)] Equation (2) states a0/α ∼ λA, where λA is called the wavelength of the first atomic dipole transition. For hydrogen, a0/α ≈ 137 a0 while the 1s-2p wavelength is approximately 2300 a0, so the stated order-of-magnitude relation does not hold unless a reduced wavelength or another definition is intended; the notation should be clarified.
- [Considerations beyond Lifshitz theory, Eq. (10)] The derivation leading to Eq. (10) yields the first-order correction -C/z^3 (1 + 3z0/z), and then the Reply writes '= -C/(z - z0)^3 + ...'. The displayed equations justify only the first-order term; the replacement 1/z^3 → 1/(z - z0)^3 is the standard Zaremba-Kohn procedure, but the text should state explicitly that this is a resummation proposed in Ref. [2] rather than an exact consequence of the preceding derivation.
Circularity Check
Reply's defense of the short-range upper limit rests on the author's own Ref. [4], whose derivation and numerics are not reproduced.
-
self citation load bearing
[Considerations within Lifshitz theory, Eq. (3) and the surrounding text]
"We have recently shown [4] that the condition for the upper limit of the short-range regime is more precisely given by z ≪ χ a0/α, χ = sqrt(αa.u.(0)/Z), ... We have performed extensive numerical calculations to support the condition (3), as detailed in Ref. [4]."
The Reply uses Eq. (3) to rebut the Comment's upper-limit condition d << z << λ0, concluding that λ0 is an 'excessively large' estimate and that the ranges indicated in Ref. [3] are correct. Eq. (3) and the supporting breakdown distances (201 a0 for hydrogen, 1300 a0 for metastable helium on gold) are not derived or numerically reproduced in this Reply; the text only states that they are 'detailed in Ref. [4]'. Ref. [4] has overlapping authorship with the Reply (T. Das, C. A. Ullrich, and U. D. Jentschura), so the central refutation of the Comment's short-range upper-limit criticism is a load-bearing self-citation chain rather than an argument or externally reproduced calculation presented in the Reply. Without Eq. (3), the Reply does not show that the Comment's upper limit misfires.
full rationale
The Reply contains one load-bearing self-citation: the refutation of the Comment's upper limit for the short-range regime is based on Eq. (3) and on breakdown distances quoted from Ref. [4], a prior paper with overlapping authorship, and the derivation and numerical support are not reproduced here. This makes the Reply's first conclusion, that the ranges in Ref. [3] are correct, depend on the author's own prior work. The other major component, the reference-plane extension of Lifshitz theory into the physisorption range, is not circular: the Reply explicitly reconstructs the Zaremba-Kohn derivation (Eqs. (6)-(12)) and cites independent literature, so that part of the defense has external grounding. The physisorption numbers themselves are applications of external formalisms and do not reduce to the Reply's own inputs by construction. The score reflects that the central range-validity claim leans on a self-citation without independent verification in this text, but the manuscript also contains substantial non-circular material, so the overall circularity is moderate rather than total.
Assumptions & free parameters
assumptions (5)
- domain assumption Zero-temperature (T=0) non-thermal field theory is the appropriate framework for the atom-surface interaction.
- domain assumption The reference-plane replacement 1/z^3 to 1/(z-z0)^3 extends Lifshitz theory into the physisorption range.
- ad hoc to paper The condition z << chi a0/alpha is the correct upper limit of the short-range expansion.
- domain assumption Lifshitz theory with the solid modeled as a continuous medium filling a half-space is valid for the systems considered.
- standard math The continuum-limit conversion of the momentum sum to an integral in Eq. (9) is valid.
Cite this review
Pith. "Pith review of Reply to Comment on "Revisiting the divergent multipole expansion of atom-surface interactions: Hydrogen and positronium, alpha-quartz, and physisorption" (arXiv:2501.14803)." pith.science (2026). https://pith.science/paper/HAQDFVQP
@misc{pith2026250213971,
author = {Pith},
title = {Pith review of: Reply to Comment on "Revisiting the divergent multipole expansion of atom-surface interactions: Hydrogen and positronium, alpha-quartz, and physisorption" (arXiv:2501.14803)},
year = {2026},
howpublished = {\url{https://pith.science/paper/HAQDFVQP}},
note = {Machine review of arXiv:2502.13971}
}
read the original abstract
We present a Reply to the Comment by G. L. Klimchitskaya, arXiv:2501.14803 [physics.atom-ph]. It is shown that the criticism formulated in the Comment fails to appreciate recently obtained results for the upper limit of the short-range expansion of atom-surface interactions, and that the application of our results to physisorption is based on a valid extension of Lifshitz theory to the physisorption range, which can be accomplished by refining the concept of the atom-surface distance with the help of a reference-plane that takes the response function of the solid into account. Some details on the calculation of the reference-plane are recalled from the literature.
Reference graph
Works this paper leans on
-
[4]
E. Zaremba and W. Kohn, Van der Waals interaction between an atom and a solid surface , Phys. Rev. B 13, 2270–2285 (1976)
work page 1976
-
[3]
G. L. Klimchitskaya, Comment on “Revisiting the di- vergent multipole expansion of atom-surface interac- tions: Hydrogen and positronium, α -quartz, and ph- ysisorption ”, Phys. Rev. A 111, 016801 (2025), available at https://arxiv.org/abs/2501.14803 [physics.atom- ph]
work page Pith review arXiv 2025
-
[1]
differs from the condi- tion z ≪ a0/α indicated in the text following Eq. (22) of Ref. [3]. (Here, α is the fine-structure constant.) First, it is interesting to observe that, in Eq. (2) of Ref. [13], the applicability of the short-range expansion is assumed to be a0 ∼ d ≪ z ≪ a0 α ∼ λA , (2) where λA is the wavelength of the first atomic (dipole) transition...
-
[2]
repulsive nearest-neighbor repulsion energy
indicates an upper limit for the applicability of the nonretarded regime which is excessively large. As shown in Ref. [4], retardation effects set in earlier than implied by the condition ( 1). The Comment then indicates that the long-range, 1 /z4 asymptotics are valid in the regime λ0 ≪ z ≪ ℏc kBT ≈ 7.6 µm . (4) Upon the modification λ0 → χ a0/α, we agree ...
-
[5]
U. D. Jentschura, Revisiting the Divergent Multipole Ex- pansion of Atom–Surface Interactions: Hydrogen and Positronium, α –Quartz, and Physisorption , Phys. Rev. A 109, 012802 (2024)
work page 2024
-
[6]
T. Das, C. A. Ullrich, and U. D. Jentschura, Retardation Effects in Atom-Wall Interactions , Phys. Rev. A 109, 022808 (2024)
work page 2024
-
[7]
E. M. Lifshitz, The Theory of Molecular Attractive Forces between Solids , Zh. ´Eksp. Teor. Fiz. 29, 94–110 (1955), [Sov. Phys. JETP 2, 73–83 (1956)]
work page 1955
-
[8]
L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media, Volume 8 of the Course on Theoreti- cal Physics (Pergamon Press, Oxford, UK, 1960)
work page 1960
Show all 40 references
-
[9]
I. E. Dzyaloshinskii, E. M. Lifshitz, and L. P. Pitaevskii, The general theory of van der Waals forces , Sov. Phys. Usp. 73, 153–176 (1961)
1961
-
[10]
I. E. Dzyaloshinskii, E. M. Lifshitz, and L. P. Pitaevskii, The general theory of van der Waals forces , Adv. Phys. 29, 165–209 (1961)
1961
-
[11]
V. A. Parsegian, Formulae for the electrodynamic inter- action of point particles with a substrate , Mol. Phys. 27, 1503–1511 (1974)
1974
-
[12]
Spruch and Y
L. Spruch and Y. Tikochinsky, Elementary approximate derivations of some retarded Casimir interactions involv- ing one or two dielectric walls , Phys. Rev. A 48, 4213– 4222 (1993)
1993
-
[13]
Tikochinsky and L
Y. Tikochinsky and L. Spruch, Retarded Casimir inter- action in the asymptotic domain of an electron and a dieletric wall , Phys. Rev. A 48, 4223–4235 (1993)
1993
-
[14]
Tikochinsky and L
Y. Tikochinsky and L. Spruch, Retarded electric and magnetic Casimir interaction of a polarizable system and a dielectric permeable wall , Phys. Rev. A 48, 4236–4244 (1993)
1993
-
[15]
Cr´ epin, R
P.-P. Cr´ epin, R. Gu´ erout, and S. Reynaud, Improved effective range expansion for Casimir–Polder potential , Eur. Phys. J. D 73, 256 (2019)
2019
-
[16]
A. O. Caride, G. L. Klimchitskaya, V. M. Mostepanenko, and S. I. Zanette, Dependences of the van der Waals atom-wall interaction on atomic and material properties , Phys. Rev. A 71, 042901 (2005)
2005
-
[17]
Bordag, G
M. Bordag, G. L. Klimchitskaya, U. Mohideen, and V. M. Mostepanenko, Advances in the Casimir Effect (Oxford University Press, Oxford, UK, 2009)
2009
-
[18]
L. W. Bruch, M. W. Cole, and E. Zaremba, Physical Adsorption: Forces and Phenomane (Dover Publications, New York, NY, 1997)
1997
-
[19]
Liebsch, Electronic Excitations at Metal Surfaces (Springer, New York, NY, 1997)
A. Liebsch, Electronic Excitations at Metal Surfaces (Springer, New York, NY, 1997)
1997
-
[20]
N. D. Lang and W. Kohn, Theory of Metal Surfaces: Work Function, Phys. Rev. B 3, 1215–1223 (1971)
1971
-
[21]
N. D. Lang and W. Kohn, Theory of Metal Surfaces: Induced Surface Charge and Image Potential , Phys. Rev. B 7, 3541–3350 (1973)
1973
-
[22]
P. J. Feibelman, Exact microscopic theory of surface con- tributions to the reflectivity of a jellium solid , Phys. Rev. B 14, 762–771 (1976)
1976
-
[23]
Bagchi, R
A. Bagchi, R. G. Barrera, and A. K. Rajagopal, Pertur- bative approach to the calculation of the electric field near a metal surface , Phys. Rev. B 20, 4824–4838 (1979)
1979
-
[24]
P. J. Feibelman, Interpretation of differential reflectance studies of metal surfaces , Phys. Rev. B 23, 2629–2634 (1981)
1981
-
[25]
B. N. J. Persson and E. Zaremba, Reference-plane position for the atom-surface van der Waals interac- tion, Phys. Rev. B 30, 5669–5679 (1984), [Erratum Phys. Rev. B 32, 6916(E) (1985)]
1984
-
[26]
B. N. J. Persson and P. Apell, Sum rules for surface re- sponse functions with application to the van der Waals interaction between an atom and a metal , Phys. Rev. B 10, 6058–6065 (1983)
1983
-
[27]
B. N. J. Persson and E. Zaremba, Electron-hole pair pro- duction at metal surfaces , Phys. Rev. B 31, 1863–1872 (1985)
1985
-
[28]
Liebsch, Density-functional calculation of the dynamic image plane at a metal surface: Reference-plane position of He- and H 2-metal van der Waals interaction , Phys
A. Liebsch, Density-functional calculation of the dynamic image plane at a metal surface: Reference-plane position of He- and H 2-metal van der Waals interaction , Phys. Rev. B 33, 7249–7251 (1986)
1986
-
[29]
Tao and A
J. Tao and A. M. Rappe, Physical Adsorption: Theory of van der Waals Interactions between Particles and Clean Surfaces, Phys. Rev. Lett. 112, 106101 (2014)
2014
-
[30]
Grimme, Accurate Description of van der Waals Com- plexes by Density Functional Theory Including Empirical Corrections, J
S. Grimme, Accurate Description of van der Waals Com- plexes by Density Functional Theory Including Empirical Corrections, J. Comput. Phys. 25, 1463–1473 (2004)
2004
-
[31]
Grimme, Semiempirical GGA-Type Density Func- tional Constructed with a Long-Range Dispersion Cor- rection, J
S. Grimme, Semiempirical GGA-Type Density Func- tional Constructed with a Long-Range Dispersion Cor- rection, J. Comput. Phys. 27, 1787–1799 (2006)
2006
-
[32]
I. P. Grant, Relativistic atomic structure: past, present and future , J. Phys. B 43, 074033 (2010)
2010
-
[33]
J. L. F. Da Silva and C. Stampfl, Trends in adsorp- tion of noble gases He, Ne, Ar, Kr, and Xe on Pd (111)( √ 3× √ 3)R30◦: All-electron density-functional cal- culations, Phys. Rev. B 77, 045401 (2008)
2008
-
[34]
D.-L. Chen, W. A. Al-Saidi, and J. K. Johnson, The role of van der Waals interactions in the adsorption of noble gases on metal surfaces , J. Phys. Conf. Ser. 24, 424211 (2012)
2012
-
[35]
P. L. Silvestrelli, A. Ambrosetti, S. Grubisiˆ c, and F. An- cilotto, Adsorption of rare-gas atoms on Cu(111) and Pb(111) surfaces by van der Waals corrected density functional theory , Phys. Rev. B 85, 165405 (2012)
2012
-
[36]
U. D. Jentschura and G. S. Adkins, Quantum Electro- dynamics: Atoms, Lasers and Gravity (World Scientific, Singapore, 2022)
2022
-
[37]
M. O. Scully and M. S. Zubairy, Quantum Optics (Cam- bridge University Press, Cambridge, UK, 1997)
1997
-
[38]
U. D. Jentschura and C. H. Keitel, Radiative Correc- tions in Laser–Dressed Atoms: formalism and applica- tions, Ann. Phys. (N.Y.) 310, 1–55 (2004)
2004
-
[39]
U. D. Jentschura and C. Moore, Logarithmic terms in atom-surface potentials: Limited applicability of ration al approximations for intermediate distance , Phys. Rev. A 108, 012815 (2023)
2023
-
[40]
J. P. Perdew, K. Burke, and M. Ernzerhof, Generalized Gradient Approximation Made Simple , Phys. Rev. Lett. 77, 3865–3868 (1996), [Erratum Phys. Rev. Lett. 78, 1396(E) (1997)]
1996
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