Resonance nuclear excitation of the $^{229}$Th nucleus via electronic bridge process in Th~II

V. A. Dzuba; V. V. Flambaum

REVIEW 4 major objections 5 minor 1 cited by

Resonance nuclear excitation of the $^{229}$Th nucleus via electronic bridge process in Th~II

T0 review · 4 major / 5 minor · reviewed 2026-08-09 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Near-resonant Th+ electron levels let a two-step laser drive the 8.4 eV 229Th nuclear transition via the electronic bridge, with up to 5-million-fold enhancement and a candidate decay shortening that could explain the thorium puzzle.

desk verdict Finds real near-degeneracies in measured Th II levels that make concrete two-laser EB excitation schemes worth testing, but the enhancement numbers are envelopes over assignments, not predictions. read the letter →

arxiv 2502.12028 v2 pith:GDRHVM2S submitted 2025-02-03 physics.atom-ph nucl-ex

V. A. Dzuba , V. V. Flambaum This is my paper · ORCID

classification physics.atom-phnucl-ex

keywords electronicbridgeprocess229ThnuclearisomerclockThIIiontwo-steplaserexcitationhyperfineinteractionenergy-levelresonancelifetime

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper seeks to make the 8.4 eV nuclear transition of 229Th, the heart of a proposed nuclear clock, addressable by ordinary lasers. In Th+ ions, the authors identify measured electron levels that lie almost exactly one nuclear-transition energy apart, the closest being only -0.09 $cm^{-1}$ off resonance, and show that a two-step laser excitation can exploit this near coincidence through the electronic bridge: electrons absorb laser light, and the hyperfine interaction passes the energy to the nucleus. They calculate that the nuclear excitation rate can be enhanced by up to 5 million in the most favorable assignment, with median realistic cases reaching $10^{4}$ to $10^{5}$. On the decay side, one candidate assignment of a measured level at 67378.61 $cm^{-1}$ shortens the 229mTh+ lifetime by a factor R = 1.3e5, close to the R > 2e5 needed to explain the puzzling sub-10 ms lifetime observed in Th II. The paper thus supplies concrete laser frequencies, level pairs, and a statistical band of enhancement factors for experiments to test.

What carries the argument

The engine is the electronic bridge amplitude G2, a product of magnetic-dipole (or electric-quadrupole) hyperfine matrix elements and electric-dipole matrix elements divided by the energy denominator omega_ns - omega_N. When an intermediate electron level n sits almost exactly one nuclear quantum above a final electron state s, the denominator shrinks to a fraction of a $cm^{-1}$ and that single resonant term dominates the second-order amplitude. The two-step laser scheme first populates an intermediate electron state t, then applies a second laser tuned to omega2 = omega_N + Es - Et; the enhancement factors $\beta$ are obtained by averaging the squared matrix-element product x over 217 possible assignments of the unassigned measured levels t and n, reporting both the mean and the median.

What would settle it

Measure the angular momentum and magnetic moment of the Th+ level at 73637.54 $cm^{-1}$: if it is neither 3/2 nor 5/2, the $\Delta$ = -0.09 $cm^{-1}$ resonance and its claimed five-million-fold enhancement disappear, and a measurement of the 229mTh+ lifetime in Th II that exceeds 10 ms would rule out the candidate R = 1.3e5 decay assignment at 67378.61 $cm^{-1}$.

Watch

Extended reading notes

Core claim

The central claim is that the electronic bridge in Th II is not just a theoretical possibility but a resonant, experimentally reachable one. Using the measured Th+ spectrum, specific pairs of electron states are identified for which the energy denominator $\Delta$ = En - Es - omega_N is near zero, making the second-order hyperfine-plus-electric-dipole amplitude dominate. With the first laser fixed at Et = 36390.53 $cm^{-1}$ and the second laser at omega2 = omega_N + Es - Et, the nuclear excitation probability is enhanced by $\beta$, with the strongest identified case giving $\Delta$ = -0.09 $cm^{-1}$ and a median $\beta$ of 1.6e5 for the M1 channel (mean 5.5e6). For the decay side, taking the measured level at 67378.61 $cm^{-1}$ as the intermediate state and calibrating calculated energies to it, one candidate assignment (state 81, J = 5/2) yields R = 1.3e5, which is within a factor of two of the R > 2e5 required to explain the observed short isomer lifetime. The authors are explicit that these factors are averages and medians over 217 possible assignments because the calculated and measured high-lying levels cannot yet be matched uniquely.

Load-bearing premise

Everything hinges on the assumption that the measured Th+ levels near the nuclear energy can be mapped onto the calculated wave functions well enough that the tiny energy denominators and matrix elements are meaningful; the paper itself states that the uncertainty in the calculated energy levels exceeds the spacing between the measured levels.

Editorial extensions

If this is right

The table specifies six second-laser frequencies, such as 37247.10 cm^-1 for the tightest resonance, at which trapped Th+ experiments can search for nuclear excitation.
If the median beta values of 10^4 to 10^5 are realized, the electronic bridge becomes a practical laser-excitation route for the 229Th nuclear clock transition.
If the 67378.61 cm^-1 level is identified as calculated state 81 with J = 5/2, the isomer lifetime in Th II shortens by R = 1.3e5, nearly matching the R > 2e5 needed for the observed sub-10 ms lifetime.
Because the resonance cross section contains the total width in its denominator, the usable enhancement saturates near beta ~ 2e5 under the inferred isomer width Gamma_Ni > 100 Hz, so the predicted factors are not automatically quenched.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

A decisive next step would be measuring the angular momenta and magnetic moments of Th II levels near 67000-77000 cm^-1; a single unambiguous assignment would collapse the 217-assignment spread into a definite beta and either confirm or eliminate the five-million-fold case.
The same two-step bridge search could be extended to Th III or Th IV when comparable level data become available, where lower level densities may make state identification easier and predictions sharper.
The statistical median-versus-mean strategy could be sharpened by using measured E1 lifetimes of the final states to constrain configuration mixing, thereby narrowing which large-matrix-element assignments are physically plausible.
A trapped-ion experiment that measures both excitation and decay on the same levels could directly test whether the short 229mTh+ lifetime and the enhanced excitation rate share the same electronic-bridge origin.

Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Colleague,

This paper does one concrete thing: it takes the measured Th II level list from Meier et al. 2019, looks for electron level pairs whose spacing is close to the 8.4 eV nuclear transition, and finds a striking near-degeneracy: Delta = -0.09 cm^-1 for the 73637.54 cm^-1 level against the 4P1/2 state at 6244.29 cm^-1. That is new, and it gives the experimental community a specific two-laser recipe (omega1 = 36390.53, omega2 = 37247.10 cm^-1) to try. The qualitative claim, that near-resonances in this energy region make large electronic-bridge enhancement plausible, is supported by the measured spectrum plus standard perturbation theory. The authors also handle the saturation issue correctly: when beta gets large, the resonance cross section stops growing because the total width becomes dominated by the EB-broadened radiative width; they note the beta ~ 2e5 cutoff from the <10 ms isomer lifetime hint. That is a real physical point and they state it plainly.

The soft spots are the ones the paper itself admits. High-lying Th II levels cannot be matched to calculated wave functions; the calculated energy uncertainty is larger than the level spacing. The headline beta = 5.5e6 sits on one assumption, Jn=3/2 for the 73637.54 cm^-1 level, and if that level is 5/2 the same row drops to 1.2e4. The median column (xm) is more honest as a representative value, and even that spans 4 to 1.6e5 across rows. The decay-side R = 1.3e5 comes from a single candidate (calculated state 81) shifted by 1153 cm^-1 to sit 14.73 cm^-1 below the nuclear energy; that is a calibration choice, not a prediction. The paper says 'consistent with' rather than 'explains', which is the right framing.

On balance the central physics is standard, the database work is real, and the specific frequencies are falsifiable in principle. The paper is not overclaiming: it gives the enhancement range and states the assignment limitation explicitly in Sec. III. The main value is as a prompt for experiments: measure J values and magnetic moments of those levels, then revisit. The level-assignment fragility is not a hidden flaw; it is the stated state of the art.

Recommendation: engage. This deserves a serious referee. I would bring it to a reading group focused on the nuclear clock program; the specific level lists and denominators are worth knowing even if the beta numbers are envelopes.

Referee Report

4 major / 5 minor

Summary. The paper proposes a two-step laser excitation scheme for resonantly driving the 8.4 eV nuclear transition in 229Th via the electronic bridge (EB) process in Th II. Using measured Th+ energy levels from Ref. [31], the authors identify near-degeneracies between electronic and nuclear excitation energies, the smallest being Δ = -0.09 cm^-1. They compute EB enhancement factors β with ab initio CI+SD/RPA methods, reporting values up to 5.5×10^6 for one angular-momentum assumption and median values of 10^4–10^5. On the decay side, they compute the EB contribution to the isomer decay rate R, finding a maximum R = 1.3×10^5 for one candidate assignment, close to the R > 2×10^5 needed to explain the sub-10 ms isomer lifetime in Th II. The paper explicitly acknowledges that measured high-lying levels cannot currently be matched to calculated wave functions and therefore presents a statistical analysis over 217 possible assignments.

Significance. The paper's qualitative claim—that measured Th+ levels near 70,000 cm^-1 contain near-degeneracies with the nuclear transition and that the EB enhancement can be large—is supported by the data and the calculations. The concrete laser frequencies and level pairs identified in Table I are potentially valuable experimental targets. A clear strength is the use of independently measured energy levels (Ref. [31]) rather than fitting the target results. However, the quantitative enhancement factors are conditional on unresolved angular-momentum assignments and on a calibration shift in the decay calculation, so the headline numbers are scenario-dependent rather than unique predictions. If these uncertainties are properly framed, the paper offers a useful step toward EB-driven nuclear excitation experiments.

major comments (4)

[Sec. III, Table I (row 1)] The abstract and conclusion highlight a '5 million times' enhancement, but this value (β = 5.5×10^6) is obtained only for Jn = 3/2 of the 73637.54 cm^-1 level. For the same level with Jn = 5/2, Table I gives β = 1.2×10^4, a factor of about 460 smaller. Since Jn has not been measured, the headline claim is not robust; a single angular-momentum measurement could substantially reduce the projected enhancement, and the paper should present the allowed range as the primary quantitative result.
[Sec. III and Appendix A] The paper states that the uncertainty in calculated energies exceeds the spacing between measured levels and that no definitive identification of states t and n is possible. Yet the quoted β values depend on matrix elements between specifically assigned states, and the median over 217 unweighted assignments is not a probability. The statement that 'the most probable cases correspond to β(xm)' is therefore not justified; xm is a summary statistic of an unweighted distribution, and the spread within Table I (e.g., β(⟨x⟩) vs β(xm) differing by up to three orders of magnitude) shows how sensitive the predictions are to the assignment model.
[Sec. IV, Table II] The largest decay enhancement, R = 1.3×10^5, rests on a single candidate identification: calculated state 81 (Jn = 5/2, 68531 cm^-1) is shifted down by 1153 cm^-1 to match the measured 67378.61 cm^-1 level, producing the small denominator Δ = 14.73 cm^-1. If that measured level has a different J or corresponds to a different calculated state, the largest R in Table II falls to ~2×10^4 or below. The paper's conclusion that EB 'may potentially explain' the thorium puzzle is appropriately cautious, but the abstract's statement that the interaction 'significantly shortens the lifetime' should carry the same explicit conditionality.
[Sec. III, Eq. (7) and Sec. IV] The argument that the EB enhancement is not saturated relies on the experimental indication Γ_Ni > 100 Hz (from τ < 10 ms in Th II). However, the paper also proposes EB as a mechanism that could produce that same short lifetime. Using the observed short lifetime both as an input to justify large β and as a target to be explained by large R introduces a mild circularity. The authors should clearly separate these two roles and note that if the EB contribution to decay is actually as large as R = 1.3×10^5, the excitation-enhancement analysis may need to self-consistently include the enhanced width.

minor comments (5)

[Sec. II, line 1] Typo: 'the Th II anf Th III ions' should read 'the Th II and Th III ions'.
[Sec. III, first paragraph] The phrase 'E /greaterorsimilarωN /2' contains a broken symbol; it should be formatted as 'E ≳ ωN/2'.
[Reference [31]] The author list contains 'P. G/suppress lowacki', which appears to be an OCR artifact for 'P. Głowacki'.
[Table I] The column entries such as '6 d27s 4P1/2' would be clearer with standard spectroscopic notation, e.g., 6d^2 7s ^4P_{1/2}.
[Sec. III, around Eq. (7)] The notation Γ_N is used for the bare nuclear width, while Γ_Ni is the width in the ion; the distinction should be stated explicitly at first use of Γ_N in Eq. (7) to avoid confusion.

Circularity Check

0 steps flagged · score 0.0 of 10

No circular derivation found: the resonant denominators and matrix elements are independent inputs, and the paper's own caveats about level assignment are uncertainty, not circularity.

full rationale

The central EB enhancement factor beta is computed from Eqs. (3) and (5), where beta is proportional to |<s||Tk||n><n||D||t>/(omega_ns - omega_N)|^2. The energy denominators use measured Th+ levels from Ref. [31] (an independent experimental group) and the known nuclear transition frequency omega_N, while the numerators are ab initio CI+SD/RPA matrix elements evaluated for candidate assignments. Nothing in this chain is fitted to the claimed enhancement values. The paper explicitly states in Sec. III and Appendix A that measured levels near 70000 cm^-1 cannot yet be matched to calculated wave functions, and it therefore reports averages and medians over 217 assignments rather than presenting a single assigned state as a definitive prediction. The decay-side quantity R in Table II is obtained by shifting a calculated state energy to reproduce the measured 67378.61 cm^-1 level; the small denominator 14.73 cm^-1 is inherited from that measured level and the known isomer energy, not manufactured by the shift. Presenting the largest R from a scan of candidate states is a selection/robustness caveat, acknowledged by the wording 'cannot entirely exclude this scenario', not a circular reduction. Self-citations to Refs. [20], [25], and [28] are methodological or background support and are not load-bearing: the computational method is implemented in the present paper and the resonant level positions come from external measurements. The main scientific risk is assignment uncertainty, which the authors disclose and quantify; this is a correctness or precision concern, not circularity.

Assumptions & free parameters 3 free parameters · 6 assumptions · 0 invented entities

The central numbers rest on three classes of inputs: (1) measured Th+ level energies and J ranges from Ref [31] and NIST [32], which are external and not supplied; (2) the authors' CI+SD/RPA calculations for matrix elements, whose accuracy near 70000 cm^-1 is validated only indirectly; (3) the ad hoc shift procedure that pins calculated spectra to the measured 67378.61 cm^-1 level and the statistical choice of reporting <x> versus xm. No new physical entities are introduced. The heavier the reliance on (2) and (3), the wider the gap between the headline numbers and the evidence.

free parameters (3)

Common energy shift DeltaEn in the decay calculation = 115 to 4771 cm^-1 depending on candidate state (Table II)
Every candidate calculated state in the 67000-72000 cm^-1 window is shifted so that it exactly hits the measured 67378.61 cm^-1 level; all other intermediate states shift by the same amount. This calibration sets the 14.73 cm^-1 denominator that drives R.
Angular momentum assignment Jn of measured high-lying levels = e.g., Jn = 3/2 or 5/2 for the 73637.54 cm^-1 level; Jn = 7/2 excluded in the decay sum
Measured levels near 70000 cm^-1 have only a range of possible J values; beta changes by up to a factor of ~460 depending on the choice (Table I rows 1 vs 2), and excluding Jn = 7/2 is a modeling decision.
Reporting statistic for the matrix-element product x = <x> (mean) and xm (median) over 217 assignments, differing by factors of 10-1000
The central beta values are quoted at both statistics; the choice of which to quote is not derived from an error model, and the headline 5.5e6 uses <x>.

assumptions (6)

domain assumption The electronic bridge amplitude is dominated by a single intermediate state n with a small energy denominator (truncation after one term in Eq. 3)
Used throughout Sections II-III; the resonance condition justifies keeping one state, but interference from other intermediate states is neglected in Eq. (3).
domain assumption Hyperfine coupling (magnetic dipole M1 and electric quadrupole E2) is the only electron-nucleus interaction mediating the bridge
Standard for the EB process; the M1/E2 width ratio gamma = 6.9e-10 is imported from Ref [34] and used to combine channels.
domain assumption CI+SD with RPA-generated effective operators yields reliable matrix elements for Th II states near 70000 cm^-1
Appendix A; only indirectly validated, since the paper reports calculated energies run ~3000 cm^-1 high near 60000 cm^-1.
ad hoc to paper A common energy shift applied to all calculated intermediate states preserves relative spacing and produces realistic energy denominators
Section IV shift procedure; the offset (up to ~4800 cm^-1) is large relative to the 14.73 cm^-1 denominator it creates.
domain assumption The measured Th+ level list of Ref [31] is complete and correct in the 67000-77000 cm^-1 window, and the quoted J ranges are exhaustive
The entire resonance search is built on these tables; Sec. V calls for a search for additional electronic levels near omegaN.
domain assumption Inputs for the bare isomer width GammaN ~ 5e-4 Hz and the < 10 ms lifetime bound for 229mTh+ (GammaNi > 100 Hz) are correct
Used in the saturation argument (Sec. III, Eq. 7) and the thorium puzzle bound R > 2e5 (Sec. IV, Ref [41]).

how reviews work

0 comments

Cite this review

Pith. "Pith review of Resonance nuclear excitation of the $^{229}$Th nucleus via electronic bridge process in Th~II." pith.science (2026). https://pith.science/paper/GDRHVM2S

@misc{pith2026250212028,
  author       = {Pith},
  title        = {Pith review of: Resonance nuclear excitation of the $^229$Th nucleus via electronic bridge process in Th~II},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/GDRHVM2S}},
  note         = {Machine review of arXiv:2502.12028}
}

abstract

The 8.4 eV transition in the $^{229}$Th nucleus is the basis for a high-precision nuclear clock with exceptional sensitivity to new physics effects. We have identified several cases in the Th$^+$ ion where electronic excitations closely resonate with the nuclear excitation, with the smallest energy difference being $\Delta = -0.09$ cm$^{-1}$. We investigate the electronic bridge process, in which nuclear excitation is induced via electronic transitions, and demonstrate that a proper selection of laser frequencies can lead to a dramatic enhancement of this effect. Additionally, we show that the interaction with electrons significantly shortens the lifetime of the nuclear excited state.

Figures

Figures reproduced from arXiv: 2502.12028 by the authors.

**Figure 2.** FIG. 2. An EB contribution to the decay rate of the isomeric [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Using the Th III Ion for a Nuclear Clock and Searches for New Physics
physics.atom-ph 2024-12 conditional novelty 6.0 of 10

Predicted 10,000-fold electronic-bridge enhancement for exciting the 229Th nuclear clock transition in Th III, plus a 1.7-times lifetime reduction and strong new-physics sensitivity factors.

Reference graph

Works this paper leans on

50 extracted references · 47 canonical work pages · cited by 1 Pith paper

[31]

Meier, J

D.-M. Meier, J. Thielking, P. G/suppress lowacki, M. V. Okhapkin, R. A. Mueller, A. Surzhykov, and E. Peik. Electronic level structure of Th+ in the range of the 229mTh isomer energy. Phys. Rev. A 99, 052514 (2019)

work page 2019
[1]

L. A. Kroger and C.W. Reich, Features of the low-energy level scheme of 229Th as observed in the α -decay of 233U, Nuclear Physics A 259, 29 (1976)

work page 1976
[2]

Peik and Chr

E. Peik and Chr. Tamm, Nuclear laser spectroscopy of the 3.5 eV transition in Th-229, Europh. Lett. 61, 181 (2003)

work page 2003
[3]

C. J. Campbell, A. G. Radnaev, A. Kuzmich, V. A. Dzuba, V. V. Flambaum, and A. Derevianko, Single-Ion Nuclear Clock for Metrology at the 19th Decimal Place, Phys. Rev. Lett. 108, 120802 (2012)

work page 2012
[4]

V. V. Flambaum. Enhancing the eﬀect of Lorentz invari- ance and Einstein equivalence principle violation in nuclei and atoms. Phys. Rev. Lett., 117, 072501 (2016)

work page 2016
[5]

V. V. Flambaum, Enhanced Eﬀect of Temporal Variation of the Fine Structure Constant and the Strong Interac- tion in 229Th, Phys. Rev. Lett. 97, 092502 (2006)

work page 2006
[6]

Asimina Arvanitaki, Junwu Huang, and Ken Van Tilburg, Searching for dilaton dark matter with atomic clocks. Phys. Rev. D 91, 015015 (2015)

work page 2015
[7]

Y. V. Stadnik and V. V. Flambaum. Can dark matter induce cosmological evolution of the fundamental con- stants of nature? Phys. Rev. Lett., 115, 201301 (2015)

work page 2015

Show all 50 references

[8]

C. W. Reich and R. G. Helmer, Energy Separation of the Doublet of Intrinsic States at the Ground State of 229Th, Phys. Rev. Lett. 64, 271 (1990)

1990
[9]

Z. O. Guimar˜ aes-Filho and O. Helen, Energy of the 3/2+ state of 229Th reexamined, Phys. Rev. C 71, 044303 (2005)

2005
[10]

B. R. Beck, J. A. Becker, P. Beiersdorfer, G. V. Brown, K. J. Moody, J. B. Wilhelmy, F. S. Porter, C. A. Kil- bourne, and R. L. Kelley, Energy Splitting of the Ground- State Doublet in the Nucleus 229Th, Phys. Rev. Lett. 98, 142501 (2007)

2007
[11]

Tiedau, M

J. Tiedau, M. V. Okhapkin, K. Zhang, J. Thielking, G. Zitzer, E. Peik, F. Schaden, T. Pronebner, I. Morawetz, L. Toscani De Col, F. Schneider, A. Leitner, M. Pressler, G. A. Kazakov, K. Beeks, T. Sikorsky, and T. Schumm. Laser excitation of the th-229 nucleus. Phys. Rev. Lett....

2024
[12]

Elwell, Christian Schneider, Justin Jeet, J

R. Elwell, Christian Schneider, Justin Jeet, J. E. S. Te r- hune, H. W. T. Morgan, A. N. Alexandrova, H. B. Tran Tan, Andrei Derevianko, and Eric R. Hudson, Laser Ex- citation of the 229Th Nuclear Isomeric Transition in a Solid-State Host, Phys. Rev. Lett. 133, 013201 (2024)

2024
[13]

Higgins, Jack F

Chuankun Zhang, Tian, Jacob S. Higgins, Jack F. Doyle, Lars von der Wense, Kjeld Beeks, Adrian Leitner, Georgy A. Kazakov, Peng Li, Peter G. Thirolf,, Thorsten Schumm and Jun Ye. Frequency ratio of the 229mTh nu- clear isomeric transition and the 87Sr atomic clock. Na- ture 63...

2024
[14]

V. F. Strizhov and E.V. Tkalya, Decay channel of low- lying isomer state of the 229Th nucleus. Possibilities of experimental investigation, Sov. Phys. JETP 72, 387 (1991)

1991
[15]

E. V. Tkalya, Excitation of low-lying isomer level of th e nucleus 229Th by optical photons, JETP Lett. 55, 211 (1992)

1992
[16]

E. V. Tkalya, Cross section for excitation of the low-lying (≤5 eV) 229Th isomer with laser radiation by the inverse electron bridge, Sov. J. Nucl. Phys. 55, 1611 (1992)

1992
[17]

F. F. Karpeshin, I. M. Band, M. B. Trzhaskowskaya, B. A. Zon. Study of 229mTh through laser-induced resonance internal conversion. Phys. Lett. B 282, 267 (1992)

1992
[18]

A. G. Porsev and V. V. Flambaum, Eﬀect of atomic elec- trons on the 7.6-eV nuclear transition in 229Th3+. Phys. Rev. A 81, 032504 (2010)

2010
[19]

S. G. Porsev and V. V. Flambaum, Electronic bridge process in 229Th+, Phys. Rev. A 81, 042516 (2010)

2010
[20]

S. G. Porsev, V. V. Flambaum, E. Peik, and Chr. Tamm, Excitation of the Isomeric 229mTh Nuclear State via an Electronic Bridge Process in 229Th, Phys. Rev. Lett.105, 182501 (2010)

2010
[22]

Lin Li, Zi Li, Chen Wang, Wen-Ting Gan, Xia Hua, Xin Tong, Scheme for the excitation of thorium 229 nuclei based on electronic bridge excitation, Nucl. Sci. Tech.34, 24 (2023). https://doi.org/10.1007/s41365-023-01169-4

2023 doi
[23]

Neng-Qiang Cai, Guo-Qiang Zhang, Chang-Bo Fu, Yu- Gang Ma, Populating 229m Th via two-photon elec- tronic bridge mechanism. Nucl. Sci. Tech. 32, 59 (2021). https://doi.org/10.1007/s41365-021-00900-3

2021 doi
[24]

Mueller, Andrey V

Robert A. Mueller, Andrey V. Volotka, and Andrey Surzhykov. Excitation of the 229Th nucleus via a two- photon electronic transition. Phys. Rev. A 99, 042517 7 (2019)

2019
[25]

V. A. Dzuba, V.V. Flambaum. Using the Th III Ion for a Nuclear Clock and Searches for New Physics, arXiv:2412.18308

arXiv
[26]

F. F. Karpeshin and M. B. Trzhaskovskaya, Excitation of the 229mTh Nuclear Isomer via Resonance Conversion in Ionized Atoms. Physics of Atomic Nuclei 78, 715 (2015)

2015
[27]

F. F. Karpeshin. Laser-assisted two-photon electron- nucleus resonance as applied to producing the 229mTh isomer. Phys. Rev. C 110, 054307 (2024)

2024
[28]

V. A. Dzuba and V. V. Flambaum. Exponential In- crease of Energy Level Density in Atoms: Th and Th II. Phys. Rev. Lett.104, 213002 (2010). DOI: 10.1103/Phys- RevLett.104.213002

2010 doi
[29]

F. F. Karpeshin, M. B. Trzhaskovskaya, A proposed solu- tion for the lifetime puzzle of the 229mTh+ isomer, Nucl. Phys. A 1010, 122173 (2021)

2021
[30]

F. F. Karpeshin, M. B. Trzhaskovskaya, Impact of the ionization of the atomic shell on the lifetime of the 229mTh isomer, Nucl. Phys. A 969 173 (2018)

2018
[32]

NIST Atomic Spectra Database (ver

Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (2024). NIST Atomic Spectra Database (ver. 5.12), [Online]. Available: https://physics.nist.gov/a sd [2024, December 15]. National Institute of Stan- dards and Technology, Gaithersburg, MD. DOI: https://doi.org/10.18434/T4W30F

2024 doi
[33]

I. I. Sobelman, Atomic Spectra And Radiative Transi- tions, (Springer-Verlag, Berlin, 1979)

1979
[34]

Bilous, Nikolay Minkov, and Adriana P´ alﬀy, Electric quadrupole channel of the 7.8 eV 229Th transi- tion, Phys

Pavlo V. Bilous, Nikolay Minkov, and Adriana P´ alﬀy, Electric quadrupole channel of the 7.8 eV 229Th transi- tion, Phys. Rev. C 97, 044320 (2018)

2018
[35]

F. F. Karpeshin and M. B. Trzhaskovskaya, Impact of the electron environment on the lifetime of the 229mTh low-lying isomer, Phys. Rev. C 76, 054313, (2007)

2007
[36]

V. V. Flambaum, Dynamical enhancement of weak inter- actions and Quantum Chaos. Proc. 85th Nobel Sympo- sium (World Scientiﬁc, 1993). Physica Scripta t46, 198 (1993)

1993
[37]

Flambaum and O

V.V. Flambaum and O. K. Vorov, Matrix elements be- tween compound states and dynamical enhancement of weak interaction. Phys. Rev. Lett. 70, 4051 (1993)

1993
[38]

V. V. Flambaum, A. A. Gribakina, G. F. Gribakin, and M. G. Kozlov, The structure of compound states in the ”chaotic” spectrum of Ce atom: localization properties, matrix elements, and enhancement of weak perturba- tions. Phys. Rev. A 50, 267 (1994)

1994
[39]

Flambaum, A.A

V.V. Flambaum, A.A. Gribakina, G.F. Gribakin and C. Harabati. Electron recombination with multicharged ions via chaoitic many-electron states. Phys. Rev. A 66, 012713(2002)

2002
[40]

J. C. Berengut, Resonant Electronic-Bridge Excitation of the 235U Nuclear Transition in Ions with Chaotic Spec- tra. Phys. Rev. Lett. 121, 253002 (2018)

2018
[41]

Thi- rolf, Lifetime Measurement of the 229Th Nuclear Isomer, Phys

Benedict Seiferle, Lars von der Wense, and Peter G. Thi- rolf, Lifetime Measurement of the 229Th Nuclear Isomer, Phys. Rev. Lett. 118, 042501 (2017)

2017
[42]

Laser spectroscopy of triply charged 229Th isomer for a nuclear clock

Atsushi Yamaguchi, Yudai Shigekawa, Hiromitsu Haba, Hidetoshi Kikunaga, Kenji Shirasaki, Michiharu Wada, and Hidetoshi Katori. Laser spectroscopy of triply charged 229Th isomer for a nuclear clock. Nature 629, 62 (2024)

2024
[43]

Controlling229Th isomeric state population in a VUV transparent crystal

Takahiro Hiraki, Koichi Okai, Michael Bartokos, Kjeld Beeks, Hiroyuki Fujimoto, Yuta Fukunaga, Hiromitsu Haba, Yoshitaka Kasamatsu, Shinji Kitao, Adrian Leit- ner, Takahiko Masuda, Ming Guan, Nobumoto Naga- sawa, Ryoichiro Ogake, Martin Pimon, Martin Pressler, Noboru Sasao, Fa...

2024
[44]

Kraemer et al

S. Kraemer et al. Observation of the radiative decay of the 229Th nuclear clock isomer. Nature 617, 706 (2023)

2023
[45]

Tkalya, Spontaneous emission probability for M1 transition in a dielectric medium: 229mTh (3/2+,3.5±1.0 eV) decay

E.V. Tkalya, Spontaneous emission probability for M1 transition in a dielectric medium: 229mTh (3/2+,3.5±1.0 eV) decay. JETP Lett. 71, 311 (2000)

2000
[46]

H. W. T. Morgan, H. B. Tran Tan, R. Elwell, A. N. Alexandrova, Eric R. Hudson, and Andrei Derevianko Theory of internal conversion of the 229Th nuclear isomer in solid-state hosts. arXiv:2411.15641

arXiv
[47]

Zhang, L

C. Zhang, L. von der Wense, J. F. Doyle, J. S. Higgins, T. Ooi, H. U. Friebel, J. Ye, R. Elwell, J. E. S. Ter- hune, H. W. T. Morgan, A. N. Alexandrova, H. B. T. Tan, A. Derevianko, and E. R. Hudson, 229ThF4 thin ﬁlms for solid-state nuclear clocks, arXiv:2410.01753

arXiv
[48]

Perera, H.W.T

U.C. Perera, H.W.T. Morgan, E.R. Hudson, A. Dere- vianko, Host-dependent frequency oﬀsets in 229Th nu- clear clockwork, arXiv:2503.20984

arXiv
[49]

V. A. Dzuba, Combination of the single-double coupled cluster and the conﬁguration interaction methods: appli- cation to barium, lutetium and their ions, Phys. Rev. A 90, 012517 (2014)

2014
[50]

W. R. Johnson, S. A. Blundell, and J. Sapirstein, Fi- nite basis sets for the Dirac equation constructed from B splines, Phys. Rev. A 37, 307 (1988)

1988
[51]

V. A. Dzuba, V. V. Flambaum, P. G. Silvestrov, and O. P. Sushkov, Correlation potential method for the calcu- lation of energy levels, hyperﬁne structure and E1 transi- tion amplitudes in atoms with one unpaired electron, J. Phys. B: At. Mol. Phys. , 20, 1399 (1987)

1987

Pith tools

Reviewed August 9, 2026 · model on record in the stance chip above.

[1] [31]

Meier, J

D.-M. Meier, J. Thielking, P. G/suppress lowacki, M. V. Okhapkin, R. A. Mueller, A. Surzhykov, and E. Peik. Electronic level structure of Th+ in the range of the 229mTh isomer energy. Phys. Rev. A 99, 052514 (2019)

work page 2019

[2] [1]

L. A. Kroger and C.W. Reich, Features of the low-energy level scheme of 229Th as observed in the α -decay of 233U, Nuclear Physics A 259, 29 (1976)

work page 1976

[3] [2]

Peik and Chr

E. Peik and Chr. Tamm, Nuclear laser spectroscopy of the 3.5 eV transition in Th-229, Europh. Lett. 61, 181 (2003)

work page 2003

[4] [3]

C. J. Campbell, A. G. Radnaev, A. Kuzmich, V. A. Dzuba, V. V. Flambaum, and A. Derevianko, Single-Ion Nuclear Clock for Metrology at the 19th Decimal Place, Phys. Rev. Lett. 108, 120802 (2012)

work page 2012

[5] [4]

V. V. Flambaum. Enhancing the eﬀect of Lorentz invari- ance and Einstein equivalence principle violation in nuclei and atoms. Phys. Rev. Lett., 117, 072501 (2016)

work page 2016

[6] [5]

V. V. Flambaum, Enhanced Eﬀect of Temporal Variation of the Fine Structure Constant and the Strong Interac- tion in 229Th, Phys. Rev. Lett. 97, 092502 (2006)

work page 2006

[7] [6]

Asimina Arvanitaki, Junwu Huang, and Ken Van Tilburg, Searching for dilaton dark matter with atomic clocks. Phys. Rev. D 91, 015015 (2015)

work page 2015

[8] [7]

Y. V. Stadnik and V. V. Flambaum. Can dark matter induce cosmological evolution of the fundamental con- stants of nature? Phys. Rev. Lett., 115, 201301 (2015)

work page 2015