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arxiv: 2505.14097 · v1 · submitted 2025-05-20 · ⚛️ physics.atom-ph · quant-ph

Carrier-envelope phase effects in one- and two-photon directional photoionization of non-isotropic atomic states

Pith reviewed 2026-05-22 14:43 UTC · model grok-4.3

classification ⚛️ physics.atom-ph quant-ph
keywords carrier-envelope phasetwo-color pulsesphotoionizationattosecond lasersphotoelectron momentum distributionsatomic orientationinterference patternscarbon atom
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The pith

The carrier-envelope phase of two-color laser pulses controls directional interference in one- and two-photon photoionization of oriented atomic states.

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

This paper examines the impact of the relative carrier-envelope phase in co- and counter-rotating two-color attosecond pulses on the one- and two-photon interference in photoelectron spectra from non-isotropic atoms, taking carbon's ground state as the prototype. A sympathetic reader would care because the directional patterns in momentum space depend on both this phase and the initial state's spatial orientation, while the one-photon region stays fixed. The work shows that photoelectron momentum distributions change with phase in the interfering channels but not in the pure one-photon part, which depends only on ellipticity, frequency, and magnetic quantum number. This difference enables extracting the phase offset simply by comparing electron ejection directions between the two channels.

Core claim

The photoelectron momentum distributions vary as a function of the carrier-envelope phase due to the interfering two-color one- and two-photon ionization paths, while the region corresponding to one-photon photoionization remains unaffected by the phase and depends only on the ellipticity of the pulse, the central photon frequency, and the magnetic quantum number of the initial state; therefore, comparing the one-photon ionization electron ejection direction with that of the two-photon channel allows extrapolation of the CEP difference between the two pulses.

What carries the argument

Interference between one-photon (2ω) and two-photon (ω+ω) ionization paths in the photoelectron momentum distribution, controlled by the relative carrier-envelope phase of the two-color pulses and the orientation of the initial electronic state.

If this is right

  • The direction of electron ejection in the two-photon ionization channel changes with the relative carrier-envelope phase.
  • The one-photon photoionization region in the momentum distribution depends only on ellipticity, frequency, and initial magnetic quantum number.
  • Comparing ejection directions between the one- and two-photon channels yields information on the CEP difference between the pulses.
  • The patterns also depend strongly on the spatial orientation of the electronic target states.

Where Pith is reading between the lines

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

  • The directional comparison method could serve as an indirect probe of relative phase in two-color attosecond experiments where direct measurement is difficult.
  • The same phase sensitivity might extend to other non-isotropic targets such as aligned molecules, offering orientation-selective ionization control.
  • Varying pulse intensity in follow-up calculations could reveal where the two-photon approximation begins to break down.

Load-bearing premise

The interference patterns can be cleanly separated into one- and two-photon channels without contamination from higher-order processes or pulse imperfections that would change the directional dependence.

What would settle it

If the one-photon region of the photoelectron momentum distribution changed with carrier-envelope phase or if the two-photon ejection directions showed no consistent relation to the phase difference, the claim that directional comparison reveals the CEP offset would not hold.

Figures

Figures reproduced from arXiv: 2505.14097 by Juan J. Omiste, Lars Bojer Madsen.

Figure 1
Figure 1. Figure 1: FIG. 1. Energy levels of the states involved in the photoion [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Photoelectron Momentum Distribution of the ground s [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Photoelectron Momentum Distribution of the ground [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Photoelectron Momentum Distribution of the ground s [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Photoelectron Momentum Distribution of the ground s [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Inclination angle of the maximum ejection, [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
read the original abstract

We study the impact of two-color ($\omega$ and $2\omega$) co- and counter-rotating ultrashort attosecond laser pulses on non-isotropic atomic targets through the one- and two-photon interference pattern of the photoelectron spectrum. Specifically, we take the ground state of atomic carbon, i. e., $(1s^22s^22p^2,{}^3\text{P}^\text{e})$ as a prototype. We observe and quantify the strong dependency on the relative carrier-envelope phase (CEP) of the two-color pulses and on the spatial orientation of the electronic target states. Notably, we observe that the photoelectron momentum distributions (PMDs) vary as a function of the CEP due to the interfering two-color one- and two-photon ionization paths. Besides, the PMD region corresponding to one-photon photoionization remains unaffected, with varying CEP, depending only on the ellipticity of the pulse, the central photon frequency and the magnetic quantum number of the initial state. Therefore, comparing the one-photon ionization electron ejection direction following absorption of a single ($2\omega$) photon with that of the two-photon ionization channel following absorption of two photon each with energy $\omega$ we may extrapolate information on the CEP difference between the two pulses.

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

2 major / 2 minor

Summary. The manuscript numerically investigates carrier-envelope phase (CEP) effects on one- and two-photon directional photoionization of the ground state of atomic carbon ((1s²2s²2p², ³Pᵉ)) driven by two-color (ω and 2ω) co- and counter-rotating attosecond pulses. It reports strong dependence of the photoelectron momentum distributions (PMDs) on relative CEP and initial-state orientation, claims that the one-photon (2ω) ionization region remains CEP-independent (depending only on ellipticity, frequency, and magnetic quantum number m), and proposes that comparing directional patterns between one- and two-photon channels allows extrapolation of the CEP difference between the pulses.

Significance. If the TDSE simulations are converged and the one- and two-photon channels can be cleanly isolated without higher-order contamination, the work would offer a potential route to CEP metrology in two-color attosecond pulses via directional photoelectron patterns from non-isotropic targets. The choice of carbon as a prototype for oriented states is reasonable, and the focus on interference between one- and two-photon paths aligns with current interests in attosecond control.

major comments (2)
  1. [Results section on PMD regions] The manuscript provides no quantitative assessment of pulse bandwidth, spectral overlap between the one-photon (2ω) and two-photon (ω+ω) channels, or the magnitude of three-photon and higher-order contributions. This separation is load-bearing for the central claim that the one-photon PMD region is strictly CEP-independent and can be used to extrapolate the relative CEP (see abstract and the PMD analysis paragraphs).
  2. [Numerical methods] No convergence tests, error estimates, or validation against known limits (e.g., single-color cases or isotropic targets) are reported for the TDSE solver. Without these, the observed directional dependencies and their CEP sensitivity cannot be verified as numerical artifacts are possible.
minor comments (2)
  1. [Abstract] Notation for the initial state and magnetic quantum number m should be introduced consistently in the abstract and main text to avoid ambiguity when discussing orientation dependence.
  2. [Figure captions] Figure captions for the PMDs should explicitly state the CEP values, pulse durations, and intensity ranges used so that the claimed independence of the one-photon region can be directly inspected.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their positive evaluation of the significance of our work and for the constructive comments. We address each major comment below and will revise the manuscript accordingly to strengthen the presentation of our results.

read point-by-point responses
  1. Referee: [Results section on PMD regions] The manuscript provides no quantitative assessment of pulse bandwidth, spectral overlap between the one-photon (2ω) and two-photon (ω+ω) channels, or the magnitude of three-photon and higher-order contributions. This separation is load-bearing for the central claim that the one-photon PMD region is strictly CEP-independent and can be used to extrapolate the relative CEP (see abstract and the PMD analysis paragraphs).

    Authors: We agree that a quantitative assessment of spectral overlap and higher-order contributions would provide stronger support for the claimed separation of channels. In the revised manuscript we will add an explicit analysis of the pulse spectra, including bandwidth estimates and the expected contribution of three-photon and higher processes at the intensities used. This addition will confirm that the one-photon momentum region remains free of significant contamination and that the CEP independence holds as stated. revision: yes

  2. Referee: [Numerical methods] No convergence tests, error estimates, or validation against known limits (e.g., single-color cases or isotropic targets) are reported for the TDSE solver. Without these, the observed directional dependencies and their CEP sensitivity cannot be verified as numerical artifacts are possible.

    Authors: We acknowledge the need for documented convergence and validation. The revised manuscript will include a new subsection (or appendix) presenting convergence tests with respect to spatial grid, time step, and basis size, together with error estimates. We will also add comparisons to single-color ionization and to isotropic targets to validate the TDSE implementation and demonstrate that the reported directional and CEP effects are physical. revision: yes

Circularity Check

0 steps flagged

No circularity: results from explicit TDSE numerics on carbon ground state

full rationale

The paper computes photoelectron momentum distributions by direct numerical integration of the time-dependent Schrödinger equation for the carbon (1s²2s²2p² ³Pᵉ) target under co- and counter-rotating ω+2ω attosecond pulses. The reported CEP dependence, the CEP-independence of the one-photon (2ω) region, and the directional comparison used to infer relative CEP are all outputs of these simulations rather than inputs. No parameter is fitted to the target directional observables, no uniqueness theorem is imported from the authors' prior work, and no ansatz is smuggled via self-citation. The separation into one- and two-photon channels follows from the model's energy conservation and pulse spectrum; it is not enforced by construction. The derivation is therefore self-contained against external numerical benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on standard quantum-mechanical treatment of laser-atom interactions with no new free parameters, axioms beyond domain assumptions, or invented entities introduced in the abstract.

axioms (1)
  • domain assumption The ground state of carbon (1s²2s²2p², ³Pᵉ) can be treated as a non-isotropic target whose magnetic substates determine directional ionization patterns under standard selection rules.
    Invoked when stating that one-photon patterns depend only on ellipticity, frequency, and magnetic quantum number.

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Reference graph

Works this paper leans on

42 extracted references · 42 canonical work pages

  1. [1]

    The PMDs are shown in Fig

    Circularly polarized laser pulse First, we consider the case of a one-color circularly polarized pulse of 10 cycles, ω = 25 eV and I = 1014 W/ cm2. The PMDs are shown in Fig. 2 for Mtot = 0 and 1. For Mtot = 0 we clearly distinguish 5 rings, la- beled as A, B, C, D and E in Fig. 2. As we have briefly discussed in Sec. II, the rings appearing in the PMD cor...

  2. [2]

    Two-color corotating laser pulse Now, we address the case of superimposing two circu- larly polarized laser pulses, specifically, ω = 25 and 50 eV with 10 and 20 cycles, respectively, such that the pulses have equal duration. First, we describe the labeling within the rings in the A B C D 0.08 0.06 0.04 0.03 0.02 0.018 0.016 0.014 0.012 0.008 0.006 0.004 −...

  3. [3]

    Two-color counter-rotating laser pulse Next, we complement the description by including the counter-rotating case, shown in Fig. 5. We keep ε = 1 for ω = 50 eV and change to ellipticity to ε = − 1 for the component with ω = 25 eV. Let us remark that the rings C and D are tilted in the opposite direction as observed in the co-rotating case [Fig. 4], since ...

  4. [4]

    95, respectively

    26 and 1 . 95, respectively. Let us remark that the dif- ferences do not correspond to exactly 2 π/ 3 due to the 7 − 2 − 1 0 1 2 3 0 π/ 10 π/ 5 3 π/ 10 2 π/ 5 π/ 2 A1 A2 A3 B1 B2 B3 αA/ B ϕ FIG. 6. Inclination angle of the maximum ejection, αAj and αBj (jth maximum) for the carbon ground state with Mtot = 1 after interacting with the counter-rotating puls...

  5. [5]

    Recent atto- clock measurements of strong field ionization,

    Adrian N. Pfeiffer, Claudio Cirelli, Mathias Smolarski, and Ursula Keller, “Recent atto- clock measurements of strong field ionization,” Chemical Physics 414, 84–91 (2013)

  6. [6]

    Attoclock with counter-rotating bicircular laser fields,

    N. Eicke and M. Lein, “Attoclock with counter-rotating bicircular laser fields,” Physical Review A 99, 031402 (2019)

  7. [7]

    Using Circular Dichroism to Con- trol Energy Transfer in Multiphoton Ionization,

    A. H. N. C. De Silva, D. Atri-Schuller, S. Dubey, B. P. Acharya, K. L. Romans, K. Foster, O. Russ, K. Compton, C. Rischbieter, N. Douguet, K. Bartschat, and D. Fischer, “Using Circular Dichroism to Con- trol Energy Transfer in Multiphoton Ionization,” Phys. Rev. Lett. 126, 023201 (2021)

  8. [8]

    Photoionization of aligned excited states in neon by attosecond laser pulses,

    J. J. Omiste and L. B. Madsen, “Photoionization of aligned excited states in neon by attosecond laser pulses,” Journal of Physics B: Atomic, Molecular and Optical Physics 54, 054001

  9. [9]

    Alternating circular dichroism in the photoelec- 8 tron spectra of the ionization of polarized atoms by ultra- short pulses,

    Ph. A. Davydiak, A. V. Meremianin, and N. L. Man- akov, “Alternating circular dichroism in the photoelec- 8 tron spectra of the ionization of polarized atoms by ultra- short pulses,” Physical Review A 111, 023113 (2025)

  10. [10]

    Electron Vortices in Photoionization by Circularly Polarized At- tosecond Pulses,

    J. M. Ngoko Djiokap, S. X. Hu, L. B. Madsen, N. L. Man- akov, A. V. Meremianin, and A. F. Starace, “Electron Vortices in Photoionization by Circularly Polarized At- tosecond Pulses,” Phys. Rev. Lett. 115, 113004 (2015)

  11. [11]

    Vortex structures in pho- todetachment by few-cycle circularly polarized pulses,

    L. Geng, F. Cajiao V´ elez, J. Z. Kami´ nski, Liang Y. Peng, and K. Krajewska, “Vortex structures in pho- todetachment by few-cycle circularly polarized pulses,” Phys. Rev. A 102, 043117 (2020)

  12. [12]

    Elliptical dichroism in biharmonic ioniza- tion of atoms,

    J. Hofbrucker, B. B¨ oning, A. V. Volotka, and S. Fritzsche, “Elliptical dichroism in biharmonic ioniza- tion of atoms,” Physical Review A 104, 013102 (2021)

  13. [13]

    Observation of the phase lag in the asymmetric photoelec- tron angular distributions of atomic barium,

    R. Yamazaki and D. S. Elliott, “Observation of the phase lag in the asymmetric photoelec- tron angular distributions of atomic barium,” Physical Review Letters 98, 053001 (2007)

  14. [14]

    Magnetic dichroism in few-photon ionization of polarized atoms,

    B. P. Acharya, M. Dodson, S. Dubey, K. L. Ro- mans, A. H.N.C. De Silva, K. Foster, O. Russ, K. Bartschat, N. Douguet, and D. Fischer, “Magnetic dichroism in few-photon ionization of polarized atoms,” Physical Review A 104, 053103 (2021)

  15. [15]

    Circular dichroism in atomic resonance-enhanced few-photon ion- ization,

    A. H. N. C. De Silva, T. Moon, K. L. Romans, B. P. Acharya, S. Dubey, K. Foster, O. Russ, C. Rischbieter, N. Douguet, K. Bartschat, and D. Fischer, “Circular dichroism in atomic resonance-enhanced few-photon ion- ization,” Physical Review A 103, 053125 (2021)

  16. [16]

    Circular dichroism in multiphoton ionization of resonantly excited helium ions near channel closing,

    R. Wagner, M. Ilchen, N. Douguet, P. Schmidt, N. Wieland, C. Callegari, Z. Delk, A. Demidovich, G De Ninno, M. Di Fraia, J. Hofbrucker, M. Manfredda, V. Music, O. Plekan, K. C. Prince, D. E. Rivas, M. Zan- grando, A. N. Grum-Grzhimailo, K. Bartschat, and M. Meyer, “Circular dichroism in multiphoton ionization of resonantly excited helium ions near channel...

  17. [17]

    Attosecond-resolved photoionization of chiral molecules,

    S. Beaulieu, A. Comby, A. Clergerie, J. Caillat, D. Descamps, N. Dudovich, B. Fabre, R. G´ eneaux, F. L´ egar´ e, S. Petit, B. Pons, G. Porat, T. Ru- chon, R. Ta ¨ ıeb, V. Blanchet, and Y. Mairesse, “Attosecond-resolved photoionization of chiral molecules,” Science 358, 1288–1294 (2017)

  18. [18]

    Pho- toexcitation circular dichroism in chiral molecules,

    S. Beaulieu, A. Comby, D. Descamps, B. Fabre, G. A. Garcia, R. G´ eneaux, A. G. Harvey, F. L´ egar´ e, Z. Maˇ s ´ ın, L. Nahon, A. F. Ordonez, S. Petit, B. Pons, Y. Mairesse, O. Smirnova, and V. Blanchet, “Pho- toexcitation circular dichroism in chiral molecules,” Nature Physics 14, 484–489 (2018)

  19. [19]

    Photo- electron momentum distributions of molecules in bichro- matic circularly polarized attosecond UV laser fields,

    K.-J. Yuan, S. Chelkowski, and A. D. Bandrauk, “Photo- electron momentum distributions of molecules in bichro- matic circularly polarized attosecond UV laser fields,” Phys. Rev. A 93, 053425 (2016)

  20. [20]

    Photoioniza- tion of triatomic molecular ions H 2+ 3 by intense bichro- matic circularly polarized attosecond uv laser pulses,

    K.-J. Yuan, H. Lu, and A. D. Bandrauk, “Photoioniza- tion of triatomic molecular ions H 2+ 3 by intense bichro- matic circularly polarized attosecond uv laser pulses,” Journal of Physics B: Atomic, Molecular and Optical Physics 50, 124004 (2017)

  21. [21]

    Alignment sensitivity of molecular- frame photoelectron momentum and angular dis- tribution of h2+ by xuv attosecond pulses,

    X. Liu, S. Gao, N. Wang, F. Zhu, L. Jiao, and A. Liu, “Alignment sensitivity of molecular- frame photoelectron momentum and angular dis- tribution of h2+ by xuv attosecond pulses,” Communications in Theoretical Physics 75, 035503 (2023)

  22. [22]

    Two-photon ion- ization of Helium studied with the multiconfig- urational time-dependent Hartree-Fock method,

    D. Hochstuhl and M. Bonitz, “Two-photon ion- ization of Helium studied with the multiconfig- urational time-dependent Hartree-Fock method,” J. Chem. Phys. 134, 084106 (2010)

  23. [23]

    Time-dependent complete-active-space self-consistent-field method for multielectron dynamics in intense laser fields,

    T. Sato and K. L. Ishikawa, “Time-dependent complete-active-space self-consistent-field method for multielectron dynamics in intense laser fields,” Phys. Rev. A 88, 023402 (2013)

  24. [24]

    Time-dependent restricted-active-space self-consistent-field the- ory for laser-driven many-electron dynamics,

    H. Miyagi and L. B. Madsen, “Time-dependent restricted-active-space self-consistent-field the- ory for laser-driven many-electron dynamics,” Phys. Rev. A 87, 062511 (2013)

  25. [25]

    Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies,

    J. J. Omiste, W. Li, and L. B. Madsen, “Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies,” Phys. Rev. A 95, 053422 (2017)

  26. [26]

    Taming molecu- lar collisions using electric and magnetic fields,

    Mark Brouard, David H. Parker, and Sebasti- aan Y. T. van de Meerakker, “Taming molecu- lar collisions using electric and magnetic fields,” Chem. Soc. Rev. 43, 7279–7294 (2014)

  27. [27]

    Quantum-state- controlled channel branching in cold Ne(3P2)+Ar chemi- ionization,

    S. D. S. Gordon, J. J. Omiste, J. Zou, S. Tan- teri, P. Brumer, and A. Osterwalder, “Quantum-state- controlled channel branching in cold Ne(3P2)+Ar chemi- ionization,” Nat. Chem. 10, 1190–1195 (2018)

  28. [28]

    Time-dependent restricted-active-space self-consistent-field sin- gles method for many-electron dynamics

    H. Miyagi and L. B. Madsen, “Time-dependent restricted-active-space self-consistent-field sin- gles method for many-electron dynamics.” J. Chem. Phys. 140, 164309 (2014)

  29. [29]

    Time-dependent restricted-active-space self-consistent-field the- ory for laser-driven many-electron dynamics. II. Extended formulation and numerical analysis,

    H. Miyagi and L. B. Madsen, “Time-dependent restricted-active-space self-consistent-field the- ory for laser-driven many-electron dynamics. II. Extended formulation and numerical analysis,” Phys. Rev. A 89, 063416 (2014)

  30. [30]

    At- tosecond photoionization dynamics in neon,

    J. J. Omiste and Lars Bojer Madsen, “At- tosecond photoionization dynamics in neon,” Phys. Rev. A 97, 013422 (2018)

  31. [31]

    CHAPTER 11 Time-dependent Restricted- active-space Self-consistent-field Theory for Elec- tron Dynamics on the Attosecond Timescale,

    L. B. Madsen, C. L´ evˆ eque, J. J. Omiste, and H. Miyagi, “CHAPTER 11 Time-dependent Restricted- active-space Self-consistent-field Theory for Elec- tron Dynamics on the Attosecond Timescale,” in Attosecond Molecular Dynamics (The Royal Society of Chemistry, 2018) pp. 386–423

  32. [32]

    Colloquium: Multiconfigurational time- dependent Hartree approaches for indistinguishable par- ticles,

    A. U. J. Lode, C. L´ evˆ eque, L. B. Madsen, A. I. Streltsov, and O. E. Alon, “Colloquium: Multiconfigurational time- dependent Hartree approaches for indistinguishable par- ticles,” Rev. Mod. Phys. 92, 011001 (2020)

  33. [33]

    Time- dependent restricted-active-space self-consistent- field theory for bosonic many-body systems,

    Camille L´ evˆ eque and L. B. Madsen, “Time- dependent restricted-active-space self-consistent- field theory for bosonic many-body systems,” New Journal of Physics 19, 043007 (2017)

  34. [34]

    Multispecies time-dependent restricted-active-space self-consisten t- field theory for ultracold atomic and molecular gases,

    Camille L´ evˆ eque and Lars Bojer Madsen, “Multispecies time-dependent restricted-active-space self-consisten t- field theory for ultracold atomic and molecular gases,” Journal of Physics B 51, 155302 (2018)

  35. [35]

    Exci- tation spectra of systems of indistinguishable par- ticles by the autocorrelation function technique: Circumventing the exponential scaling for bosons,

    Camille L´ evˆ eque and Lars Bojer Madsen, “Exci- tation spectra of systems of indistinguishable par- ticles by the autocorrelation function technique: Circumventing the exponential scaling for bosons,” The Journal of Chemical Physics 150, 194105 (2019)

  36. [36]

    Solving the time-dependent Schr¨ odinger equation using complex-coordinate contours,

    C. W. McCurdy, C. K. Stroud, and M. K. Wisin- ski, “Solving the time-dependent Schr¨ odinger equation using complex-coordinate contours,” Phys. Rev. A 43, 5980–5990 (1991)

  37. [37]

    Effects of core space and excitation levels on ground-state correla- tion and photoionization dynamics of Be and Ne,

    J.J. Omiste and L. B. Madsen, “Effects of core space and excitation levels on ground-state correla- tion and photoionization dynamics of Be and Ne,” The Journal of Chemical Physics 150, 084305 (2019)

  38. [38]

    Time-dependent 9 multiconfiguration methods for the numerical simulation of photoionization processes of many-electron atoms,

    D. Hochstuhl, C. Hinz, and M. Bonitz, “Time-dependent 9 multiconfiguration methods for the numerical simulation of photoionization processes of many-electron atoms,” The European Physical Journal Special Topics 223, 177–336 (2014)

  39. [39]

    Extracting continuum information from Ψ(t) in time-dependent wave-packet calculations,

    L. B. Madsen, L. A. A. Nikolopoulos, T. K. Kjeldsen, and J. Fern´ andez, “Extracting continuum information from Ψ(t) in time-dependent wave-packet calculations,” Phys. Rev. A 76, 063407 (2007)

  40. [40]

    Above-threshold ion- ization of helium in the long-wavelength regime: Examining the single-active-electron approximation and the two-electron strong-field approximation,

    C. Yu and L. B. Madsen, “Above-threshold ion- ization of helium in the long-wavelength regime: Examining the single-active-electron approximation and the two-electron strong-field approximation,” Phys. Rev. A 95, 063407 (2017)

  41. [41]

    R. N. Zare, Angular Momentum: Understanding Spatial Aspects in Chemistry and Physics (John Wiley and Sons, New York, 1988)

  42. [42]

    NIST Atomic Spectra Database (ver. 5.6.1) [Online],

    A. Kramida, Yu. Ralchenko, and J. Reader, “NIST Atomic Spectra Database (ver. 5.6.1) [Online],” Avail- able: https://physics.nist.gov/asd. National Insti- tute of Standards and Technology, Gaithersburg, MD. (2018)