REVIEW 3 major objections 4 minor 31 references
High-precision ab initio calculations of the spectrum of Lr$^{+}$
T0 review · 3 major / 4 minor · reviewed 2026-08-14 · deepseek-v4-flash
Pith's one-line read The paper predicts the first systematic, high-precision spectrum of Lr+, identifying two strong ground-state transitions at 31540 and 47295 cm^-1 with uncertainties of at least 389 cm^-1.
desk verdict First real Lr+ spectrum calculation, with a useful slate of atomic properties for the planned experiment—but the uncertainty bars are not as conservative as claimed, and one benchmark level sits well outside the quoted 389 cm−1 floor. 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 central device is homologue benchmarking with two independent relativistic methods: Fock space coupled cluster (FSCC), a multireference approach that builds excited states by adding electrons to a closed-shell reference, and configuration interaction plus many-body perturbation theory (CI+MBPT), which combines a CI expansion with second-order core-valence corrections. Both start from the projected Dirac-Coulomb-Breit Hamiltonian and include QED corrections through separate operators. Agreement between the two methods, validated by reproducing measured Lu+ levels and transition rates, is used to set the Lr+ error bars and to justify transferring the demonstrated accuracy to the heavier ion.
What would settle it
A laser scan of the predicted $7s7p\,{}^3P_1$ transition near $31540\,\mathrm{cm}^{-1}$ that finds no resonance within the stated uncertainty band, or finds the $7s7p\,{}^1P_1$ line at $47295\,\mathrm{cm}^{-1}$ displaced by more than the recommended uncertainty, would refute the assumption that Lu+ accuracy transfers to Lr+.
Extended reading notes
Core claim
The paper claims to provide the first large-scale systematic calculation of the Lr+ spectrum. Both methods place the ground state at $7s^2\,{}^1S_0$ and agree on the ordering of the low-lying $6d7s$ and $7s7p$ levels; the recommended energies are the mean of the FSCC and CI+MBPT results, with uncertainty at least $389\,\mathrm{cm}^{-1}$ or the inter-method difference. For the two transitions proposed for experiment, the paper gives $7s7p\,{}^3P_1$ at $31540 \pm 389\,\mathrm{cm}^{-1}$ (lifetime 14.5 ns, branching ratio 0.90 to ground) and $7s7p\,{}^1P_1$ at $47295 \pm 1048\,\mathrm{cm}^{-1}$ (lifetime 1.1 ns, branching ratio 0.96). It also finds that the $6d7s\,{}^3D_1$ level decays only by a suppressed M1 transition and has a lifetime of about 25 days. The accuracy argument rests on Lu+: average theory-experiment differences of $-263\,(348)\,\mathrm{cm}^{-1}$ for FSCC and $16\,(389)\,\mathrm{cm}^{-1}$ for CI+MBPT over the eight lowest relevant levels.
Load-bearing premise
The entire error budget for Lr+ rests on the assumption that the accuracy demonstrated for Lu+ transfers to Lr+ unchanged, since no Lr+ experimental data exists to test it.
Editorial extensions
If this is right
- Experimenters can begin a laser search by scanning a window around $31540\,\mathrm{cm}^{-1}$ for the $7s7p\,{}^3P_1$ state, the strongest accessible ground-state transition with the smallest recommended uncertainty.
- The $7s7p\,{}^1P_1$ line at $47295\,\mathrm{cm}^{-1}$, with a branching ratio of 0.96 and a lifetime near 1 ns, provides a second, independent resonance to confirm the spectrum.
- The predicted lifetimes and branching ratios allow estimates of detector sensitivity and required beam time for an experiment producing about one ion per second.
- The very long predicted lifetime of the $6d7s\,{}^3D_1$ level (about 25 days) means population can accumulate in a metastable state, which any excitation scheme must take into account or could exploit.
Reading between the lines
- The paper does not spell this out, but the same dual-method benchmarking could be used to set search windows for the next even heavier ions, where no homologous experimental anchor exists.
- A precise remeasurement of the Lu+ $3P_2$ g-factor would be a cheap indirect test of the wavefunction-quality assumption: the paper predicts 1.50 against a tabulated 1.66 and notes the assignment may be erroneous.
- The metastable $6d7s\,{}^3D_1$ state, with its 25-day lifetime, could in principle serve as an optical-clock or trapping state for Lr+ if the ion can be held long enough; this goes beyond the paper's experimental guidance.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper reports relativistic Fock-space coupled-cluster (FSCC) and CI+MBPT calculations of the low-lying excitation spectrum, g-factors, transition rates, branching ratios, and lifetimes of Lr+ and its lighter homologue Lu+. The authors benchmark both methods against experimental Lu+ energy levels and A coefficients, then use the Lu+ comparison to assign uncertainties to their recommended Lr+ energies, which are taken as the mean of the two methods with an uncertainty of max(method difference, 389 cm^-1). The main output is a set of recommended Lr+ excitation energies, of which the two strongest ground-state transitions are identified as 7s7p 3P1 at 31540 cm^-1 and 7s7p 1P1 at 47295 cm^-1, meant to guide the planned optical spectroscopy of Lr+. No experimental Lr+ data are used in the calculations.
Significance. If the predictions are reliable, this is the first systematic theoretical spectrum of Lr+ and will directly inform an ongoing experimental search, making the paper valuable to both atomic theory and superheavy-element spectroscopy. The study combines two independent state-of-the-art methods, presents explicit basis-convergence and MBPT partial-wave-convergence tests, and does not fit any Lr+ experimental data, so the recommended energies are genuinely ab initio. The Lu+ comparison is a useful validation of both methods and of the predicted A coefficients. However, the paper's central uncertainty prescription is not supported by its own benchmark, as one Lu+ level shows an error of about 550 cm^-1 while the quoted uncertainty floor is 389 cm^-1; because the experimental search window will be set by these quoted errors, this issue is load-bearing for the paper's main application.
major comments (3)
- [Section III, Table I] The uncertainty prescription described in Section III is not conservative by the paper's own Lu+ benchmark. For Lu+ 5d6s 1D2, CI+MBPT gives 17892 cm^-1 and FSCC gives 17875 cm^-1, while the experimental value is 17332 cm^-1. The recommended mean is therefore 17884 cm^-1, an error of about 552 cm^-1, yet the formula max(method difference, 389 cm^-1) assigns this level an uncertainty of only 389 cm^-1. Because 389 cm^-1 is the standard deviation of the CI+MBPT residuals, it is expected that some individual residuals exceed it; calling that value 'conservative' is contradicted by an in-sample case. This matters directly for the primary Lr+ search line at 31540 cm^-1, whose quoted ±389 cm^-1 is set by the same floor and would not cover a shared bias of the magnitude seen in Lu+.
- [Section III] Using the difference between the two calculated energies as an error estimate is not sensitive to systematic errors common to both methods. The Lu+ 5d6s 1D2 case shows that the two methods can agree to 17 cm^-1 while both being about 550 cm^-1 from experiment, so a small method difference cannot be taken as evidence of small total error. Both calculations start from the same projected Dirac-Coulomb-Breit Hamiltonian and use similar QED-model corrections, so shared systematic errors are plausible. I ask the authors to replace or supplement the max(method-difference, standard-deviation) rule with a bound that covers the observed Lu+ residuals, for example the maximum residual or an expanded uncertainty, and to discuss which physical effects could produce a common bias in Lr+ but not in Lu+.
- [Section III] The statement 'We expect similar accuracy for the calculated transition energies of the heavier homologue of Lu+, Lr+' is the only justification for transferring the Lu+ error estimate to Lr+. The paper should make this transferability argument more concrete, for example by comparing the Lr+ energies with the independent prior calculations of Dzuba et al. and Cao and Dolg, or by estimating the sensitivity of the 7s7p levels to higher-order correlation, higher partial waves, and the QED-model uncertainty. Without such a check, the quoted uncertainties for Lr+ rest on an untested assumption; this is not a fatal flaw, but it is load-bearing for the experimental search-window application.
minor comments (4)
- [Table V] In the first two rows of Table V, the lower level is labeled '7s2 2 S0' but the ground state is 7s2 1S0; the superscript should be 1.
- [Section II B] The phrase 'Land` e g-factors' contains a formatting artifact; it should read 'Landé g-factors'.
- [Section II A, Eq. (4)] The definition of the even-tempered exponents in Eq. (4) is hard to read because the value of gamma is split across lines; please format it as a single number.
- [Abstract] The hyphen in 'branching-ratios' should be removed for consistency with the main text and standard usage.
Circularity Check
No significant circularity: the Lr+ predictions are produced by two independent ab initio methods and are not fitted to any Lr+ experimental data.
full rationale
The central output of the paper, the recommended Lr+ excitation energies, is computed as the unweighted mean of FSCC and CI+MBPT results obtained from the projected Dirac-Coulomb-Breit Hamiltonian. No Lr+ experimental level is used to determine or adjust any parameter in either calculation, so the predicted energies are not equivalent by construction to the inputs. The Lu+ comparison in Table I uses independent published experimental data (refs. [29,30]) as an external benchmark, and the uncertainty prescription (max of method difference and the 389 cm-1 standard deviation of CI+MBPT Lu+ errors) is a calibration on that homologue, not a fit to the target. The self-citations (TRAFS-3C, ambit, and earlier FSCC/CI+MBPT papers) are references to the methods and codes themselves; their validity is supported by the external Lu+ agreement, so they are not load-bearing self-citations. The statement 'we expect similar accuracy' for Lr+ is an explicit transferability assumption and a limitation, not a circular step. Even if the uncertainty floor is questioned (e.g., the Lu+ 5d6s 1D2 level has a true error around 550 cm-1 at the quoted mean), that is a correctness or calibration risk, not a circularity, because the prediction does not reduce to the Lu+ data used to set the error bar.
Assumptions & free parameters
free parameters (4)
- Virtual orbital energy cutoff =
200 a.u.
- FSCC model space sizes =
13s11p9d8f6g5h (Lu+), 14s12p10d9f6g5h (Lr+)
- CI and emu CI truncations =
single excitations to 16 spdfg; single and double excitations to 12 spdfg; Ndominant threshold
- MBPT partial-wave limit =
orbitals up to 35 spdfghi (l <= 6)
assumptions (5)
- domain assumption The projected Dirac-Coulomb-Breit Hamiltonian, correct to second order in the fine-structure constant, is an adequate starting point for Lr+ and Lu+.
- domain assumption Lu+ is a valid lighter homologue whose calculation accuracy transfers to Lr+.
- domain assumption The ground state of Lr+ is 7s2 1S0.
- domain assumption Model-space, basis, and MBPT truncations are converged to the claimed accuracy.
- domain assumption The model Lamb shift operator and radiative potential adequately describe QED effects for these ions.
Cite this review
Pith. "Pith review of High-precision ab initio calculations of the spectrum of Lr$^{+}$." pith.science (2026). https://pith.science/paper/MB472OII
@misc{pith2026190804578,
author = {Pith},
title = {Pith review of: High-precision ab initio calculations of the spectrum of Lr$^+$},
year = {2026},
howpublished = {\url{https://pith.science/paper/MB472OII}},
note = {Machine review of arXiv:1908.04578}
}
abstract
The planned measurement of optical resonances in singly-ionised lawrencium (Z = 103) requires accurate theoretical predictions to narrow the search window. We present high-precision, ab initio calculations of the electronic spectra of Lr$^+$ and its lighter homologue lutetium (Z = 71). We have employed the state-of-the-art relativistic Fock space coupled cluster approach and the AMBiT CI+MBPT code to calculate atomic energy levels, g-factors, and transition amplitudes and branching-ratios. Our calculations are in close agreement with experimentally measured energy levels and transition strengths for the homologue Lu$^+$ , and are well-converged for Lr$^+$ , where we expect a similar level of accuracy. These results present the first large-scale, systematic calculations of Lr$^+$ and will serve to guide future experimental studies of this ion.
Figures
Reference graph
Works this paper leans on
- [1]
-
[2]
M. Laatiaoui, W. Lauth, H. Backe, M. Block, D. Ack- ermann, B. Cheal, P. Chhetri, C. E. D¨ ullmann, P. Van Duppen, J. Even, R. Ferrer, F. Giacoppo, S. G¨ otz, F. P. Heßberger, M. Huyse, O. Kaleja, J. Khuyagbaatar, P. Kunz, F. Lautenschl¨ ager, A. K. Mistry, S. Raeder, E. Minaya Ramirez, T. Walther, C. Wraith, and A. Yakushev, Nature 538, 495 (2016)
work page 2016
-
[3]
A. Zadvornaya, P. Creemers, K. Dockx, R. Ferrer, L. P. Gaffney, W. Gins, C. Granados, M. Huyse, Y. Kudryavt- sev, M. Laatiaoui, E. Mogilevskiy, S. Raeder, S. Sels, P. Van den Bergh, P. Van Duppen, M. Verlinde, E. Ver- straelen, M. Nabuurs, D. Reynaerts, and P. Papadakis, Phys. Rev. X 8, 041008 (2018)
work page 2018
-
[4]
O. Kaleja, B. Andeli´ c, K. Blaum, M. Block, P. Chhetri, C. Droese, C. E. D¨ ullmann, M. Eibach, S. Eliseev, J. Even, S. G¨ otz, F. Giacoppo, N. Kalantar-Nayestanaki, E. Minaya Ramirez, A. Mistry, T. Murb¨ ock, S. Raeder, and L. Schweikhard, Nuclear Instruments and Methods in Physics Research Section B , in press (2019). 6 TABLE IV. Einstein coefficients ( ...
work page 2019
-
[5]
F. Lautenschl¨ ager, P. Chhetri, D. Ackermann, H. Backe, M. Block, B. Cheal, A. Clark, C. Droese, R. Ferrer, F. Gi- acoppo, S. G¨ otz, F.-P. Heßberger, O. Kaleja, J. Khuyag- baatar, P. Kunz, A. K. Mistry, M. Laatiaoui, W. Lauth, S. Raeder, T. Walther, and C. Wraith, Nuclear Instru- ments and Methods in Physics Research Section B 383, 115 (2016)
work page 2016
- [6]
- [7]
-
[8]
E. V. Kahl and J. C. Berengut, Computer Physics Com- munications 238, 232 (2019)
work page 2019
Show all 31 references
-
[9]
V. A. Dzuba, M. S. Safronova, and U. I. Safronova, Phys. Rev. A 90, 012504 (2014)
2014
-
[10]
CAO and M
X. CAO and M. DOLG, Molecular Physics 101, 961 (2003), https://doi.org/10.1080/0026897021000046807
2003 doi
-
[11]
Fraga, Anales de Fisica 70, 249 (1974)
S. Fraga, Anales de Fisica 70, 249 (1974)
1974
-
[12]
(1) Here, hD is the one electron Dirac Hamiltonian, hD(i) =c αi · pi +c2(βi − 1) +Vnuc(i), (2) where α and β are the four-dimensional Dirac matrices
(atomic units ℏ = me = e = 1 are used throughout this work), HDCB = ∑ i hD(i) + ∑ i<j (1/rij +Bij). (1) Here, hD is the one electron Dirac Hamiltonian, hD(i) =c αi · pi +c2(βi − 1) +Vnuc(i), (2) where α and β are the four-dimensional Dirac matrices. The nuclear potential Vnuc ...
2020
-
[13]
Sucher, Phys
J. Sucher, Phys. Rev. A 22, 348 (1980)
1980
-
[14]
High-accuracy relativistic coupled-cluster calculations for the heaviest elements,
E. Eliav, A. Borschevsky, and U. Kaldor, “High-accuracy relativistic coupled-cluster calculations for the heaviest elements,” in Handbook of Relativistic Quantum Chem- istry, edited by W. Liu (Springer-Verlag Berlin Heidel- berg, 2017) pp. 819–849
2017
-
[15]
Eliav, M
E. Eliav, M. J. Vilkas, Y. Ishikawa, and U. Kaldor, J. Chem. Phys. 122, 224113 (2005)
2005
-
[16]
G. L. Malli, A. B. F. Da Silva, and Y. Ishikawa, Phys. Rev. A 47, 143 (1993)
1993
-
[17]
Shabaev, I
V. Shabaev, I. Tupitsyn, and V. Yerokhin, Computer Physics Communications 189, 175 (2015)
2015
-
[18]
V. A. Dzuba, V. V. Flambaum, and M. G. Kozlov, Phys. Rev. A 54, 3948 (1996)
1996
-
[19]
J. C. Berengut, Phys. Rev. A 94, 012502 (2016)
2016
-
[20]
J. C. Berengut, V. V. Flambaum, and M. G. Kozlov, Phys. Rev. A 73, 012504 (2006)
2006
-
[21]
Torretti, A
F. Torretti, A. Windberger, A. Ryabtsev, S. Dobrodey, H. Bekker, W. Ubachs, R. Hoekstra, E. V. Kahl, J. C. Berengut, J. R. C. L´ opez-Urrutia, and O. O. Versolato, Phys. Rev. A 95, 042503 (2017)
2017
-
[22]
A. J. Geddes, D. A. Czapski, E. V. Kahl, and J. C. Berengut, Phys. Rev. A 98, 042508 (2018)
2018
-
[23]
W. R. Johnson, Lectures on Atomic Physics (Dept. of Physics, University of Notre Dame, South Bend, IA, 1994)
1994
-
[24]
W. R. Johnson, S. A. Blundell, and J. Sapirstein, Phys. Rev. A 37, 307 (1988). 7
1988
-
[25]
Beloy and A
K. Beloy and A. Derevianko, Comp. Phys. Commun. 179, 310 (2008)
2008
-
[26]
V. V. Flambaum and J. S. M. Ginges, Phys. Rev. A 72, 052115 (2005)
2005
-
[27]
J. S. M. Ginges and J. C. Berengut, Phys. Rev. A 93, 052509 (2016)
2016
-
[28]
J. S. M. Ginges and J. C. Berengut, J. Phys. B49, 095001 (2016)
2016
-
[29]
V. A. Dzuba, J. C. Berengut, C. Harabati, and V. V. Flambaum, Physical Review A 95, 012503 (2017)
2017
-
[30]
W. C. Martin, R. Zalubas, and L. Hagan, NSRDS-NBS, Washington: National Bureau of Standards, U.S. Depart- ment of Commerce, —c1978 (1978)
1978
-
[31]
J. E. Sansonetti and W. C. Martin, Journal of Physical and Chemical Reference Data 34, 1559 (2005)
2005
Reviewed August 14, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.