Pith. sign in

REVIEW 3 major objections 5 minor 77 references

Predicting Accurate X-ray Absorption Spectra for CN$^+$, CN, and CN$^-$: Insights from Multiconfigurational and Density Functional Simulations

T0 review · 3 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash

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

Pith's one-line read Predicted carbon K-edge spectra for CN+, CN, and CN- place the first vibronic lines at 280.7, 279.6, and 285.8 eV, with the CN- absorption assigned to a doubly degenerate π* transition.

desk verdict Solid reference calculations for CN+/CN/CN- C1s XAS, but the headline 0-0 energies are anchored to BLYP via a CO+ shift rather than independently validated by the multiconfigurational wavepacket work. read the letter →

arxiv 2412.19065 v2 pith:CBJFBLS4 submitted 2024-12-26 physics.chem-ph astro-ph.HEphysics.atm-clusphysics.comp-ph

Jinyu Li , Sheng-Yu Wang , Lu Zhang , Guoyan Ge , Minrui Wei , Junxiang Zuo , Weijie Hua This is my paper · ORCID
classification physics.chem-phastro-ph.HEphysics.atm-clusphysics.comp-ph
keywords X-rayabsorptionspectroscopyvibronicfinestructurecore-holeeffectCNradicalinterstellarmoleculesmulticonfigurationalmethodsquantumwavepacketmethodcharge-stateeffects
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 tries to establish what high-resolution carbon K-edge X-ray absorption spectra of CN+, CN, and CN- should look like, since no experimental spectra exist for these interstellar species. It argues that the first electronic peak is a C1s→σ* transition in CN+ and CN but a C1s→π* transition in CN-, and that the two-fold degeneracy of the π* orbitals makes CN-'s first band roughly twice as intense. Using multiconfigurational potential energy curves and a quantum wavepacket treatment, it predicts the 0-0 vibronic lines at 280.7, 279.6, and 285.8 eV, each profile dominated by the 0-0 peak. These numbers are anchored by calibrating each method to the measured CO+ spectrum, because CO+ is isoelectronic with CN.

What carries the argument

The carrying object is a set of anharmonic potential energy curves for the ground and lowest C1s core-excited states of each species, computed at the multiconfigurational level (SA-RASSCF and MS-RASPT2) and fitted to Morse functions; the spectra are obtained by propagating a quantum wavepacket on these curves. A second load-bearing piece is the method-specific ad hoc shift δ, determined by aligning the calculated CO+ spectrum to its measured first peak and then applied, unchanged, to CN+, CN, and CN-. The Morse fits supply equilibrium distances, well depths, and force constants, and the wavepacket propagation converts those curves into the 0-0, 0-1, and 0-2 vibronic stick intensities.

What would settle it

A gas-phase carbon K-edge X-ray absorption measurement on mass-selected CN+, CN, and CN- would settle the claim by checking the 0-0 peak positions against 280.7, 279.6, and 285.8 eV and by checking that the first CN- peak is about twice as strong as the first peaks of CN+ and CN. Disagreement beyond the calibrated method accuracy, or a wrong ordering of the first peaks, would falsify the calibrated predictions.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is a set of quantitative predictions, not a measurement: vibrationally resolved C1s XAS profiles for the three charge states of CN, with assignments and peak energies. The first electronic absorption of CN+ and CN is C1s→σ*, that of CN- is C1s→π*, and the degeneracy of the π*xz and π*yz channels doubles the anion's first-peak intensity; the 0-0 energies are 280.7 eV (CN+), 279.6 eV (CN), and 285.8 eV (CN-). The calculations also show that creating a C1s core hole shortens the C-N bond by roughly 4-6 pm (6-7 pm at the DFT harmonic level) and raises the vibrational frequency by 300-400 cm−1 in all three species. The authors take the agreement among RASSCF, RASPT2, and DFT profiles, plus the calibration to CO+, as evidence that these are accurate predictions for astronomy and laboratory work.

Load-bearing premise

The whole absolute-energy scale rests on assuming that the ad hoc shift δ fitted to CO+ transfers unchanged to CN+, CN, and CN-; if the C1s core hole relaxes differently in these charge states, all predicted 0-0 energies would be off by roughly the same systematic amount while the spectral shapes would remain useful.

Editorial extensions

If this is right

  • If the predictions hold, the first carbon K-edge absorption of CN- should appear about 6 eV above those of CN+ and CN, giving observers a spectroscopic handle to separate the anion from the neutral and cation.
  • The assignment of the first peak to C1s→π* in CN- means its absorption should be roughly twice as intense as the corresponding C1s→σ* peaks, so intensity ratios can be used alongside energies for identification.
  • Each vibronic profile is dominated by the 0-0 line, so future high-resolution X-ray spectra should show a single prominent line at the predicted energy rather than a long vibrational progression.
  • The predicted bond shortening and frequency increase upon core excitation imply that vibrationally resolved spectra of all three species will shift intensity from higher vibrational levels toward the 0-0 line.

Reading between the lines

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

  • The transferability of the CO+ calibration shift is the natural thing to test: because CN- has diffuse orbitals and strong relaxation, its absolute energies may carry a larger systematic error than the 0-1 relative spacings; a high-level calculation or measurement of the anion alone would settle this.
  • If the predicted lines are confirmed, the X-ray absorption bands could be used as diagnostics of charge state in astrophysical environments where CN+, CN, and CN- coexist, paralleling how their microwave emission is already used.
  • The same wavepacket-plus-Morse machinery could be applied to other isoelectronic triads to test whether the non-monotonic energy ordering seen here is a general feature of changing charge state.
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.

Referee Report

3 major / 5 minor

Summary. The paper predicts C1s X-ray absorption spectra for the astrochemically relevant species CN+, CN, and CN- using BLYP-FCH DFT, SA-RASSCF (in both Molpro and OpenMolcas), and MS-RASPT2. Each method is calibrated by a single ad hoc shift delta derived from the CO+ experimental spectrum, under the assumption that delta transfers to the carbon-nitrogen species. The authors assign the first absorption peak to C1s -> sigma* for CN+ and CN and to C1s -> pi* for CN-, explain the larger intensity in CN- by the twofold degeneracy of pi*, and compute vibronic fine structure with a quantum wavepacket method on anharmonic Morse-fitted multiconfigurational PECs. They report 0-0 absorption energies of 280.7 eV (CN+), 279.6 eV (CN), and 285.8 eV (CN-), together with core-hole-induced bond shortening and vibrational frequency increases.

Significance. If the absolute transition energies were independently validated, this would be a valuable reference set for X-ray astronomy and laboratory spectroscopy of interstellar CN species. The paper has clear strengths: it cross-checks two independent RASSCF implementations and RASPT2, reproduces the CO+ experimental peak separation at the multiconfigurational level, uses anharmonic wavepacket dynamics rather than only harmonic Franck-Condon factors, and supplies raw PEC data in the Supplementary Material. However, the headline absolute energies are not parameter-free: they depend on a single fitted shift and, in the final spectra, on an alignment of all methods to the BLYP spectrum. The relative vibronic profiles and the peak assignments are considerably more robust than the absolute energy calibration.

major comments (3)
  1. [Section III E and Fig. 4 caption] The reported 0-0 energies of 280.7, 279.6, and 285.8 eV are not independently determined by the multiconfigurational wavepacket calculations. The Fig. 4 caption states that "all other methods were aligned to the BLYP spectrum by adjusting the 0-0 peak," and Section II B specifies that the BLYP spectrum is itself shifted by a CO+-derived delta. Consequently, the RASSCF and RASPT2 curves in Fig. 4 agree with BLYP only in relative vibronic shape, not in absolute energy. The abstract and Section III E present the three values as if they were revealed by the anharmonic wavepacket simulations on multiconfigurational PECs. Because Table I shows raw vertical excitation energies that differ by more than 1 eV between methods (for example, CN+ peak i at 282.22 eV for RASSCF/MOLPRO versus 281.01 eV for BLYP in the calibrated table), this alignment is not a negligible detail. I request either an independent calibration of delta for at least one additional species or an explicit uncertainty estimate for the 0-0 positions based on the spread of raw method-dependent energies; the current presentation overstates the evidence for the absolute values.
  2. [Section II B] The transferability of the method-specific shift delta from CO+ to CN+, CN, and CN- is assumed without quantitative support. CO+ is isoelectronic with CN, but not with CN+ or CN-, and Section III A explicitly notes that CN- has "notably different unoccupied orbitals" compared with the other systems. Core-hole relaxation, and hence the systematic error in the absolute core-excitation energy, may differ substantially for the anion. The authors should provide a test of transferability, for example by calibrating delta against an additional benchmark molecule or ion with a known C1s spectrum and by comparing unshifted RASPT2 vertical energies with BLYP across the three target species. Without such a test, the claimed accuracy of the absolute 0-0 energies, especially the CN- value of 285.8 eV, rests on a single fitted constant.
  3. [Section II B and Fig. S1] For CN-, the wide-range electronic XAS spectrum was obtained with the smaller cc-pVDZ basis set and calibrated to the main aug-cc-pVTZ peak, because the aug-cc-pVTZ calculation covered only a narrow energy window. This compromise is acknowledged, but its effect on the relative intensities of the pi* first peak and the higher-energy C-np peaks is not quantified. Since the twofold degeneracy of pi* is used to explain the pronounced first absorption of CN-, it is important to show that the two-fold intensity enhancement is not an artifact of the smaller basis or of the calibration procedure. I ask the authors to state explicitly how the basis-set compromise affects the oscillator strengths, the relative peak intensities, and the value of delta for CN-, and to show any available aug-cc-pVTZ data over the full displayed range or to provide a conservative uncertainty estimate for the affected spectral region.
minor comments (5)
  1. [Table I and Fig. 2] The manuscript's species list is inconsistent: Table I and Fig. 2 include CO and CO+, while the abstract and main text focus on CN+, CN, and CN-; please clarify in the captions and text whether CO is used only as an additional reference or is an intended target.
  2. [Section III D and Table III] The statement that the ground-state PECs "decrease in the order of CN+, CN, and CN-" is not directly supported by the Te values in Table III (for example, RASPT2 Te is 0.082 eV for both CN+ and CN); please specify the reference energy for Te so that the ordering can be checked.
  3. [Table IV] The label "non-physical shake-off processes" for the negative IPs of the core-excited CN- is confusing: a negative vertical electron-detachment energy for a core-excited anion can be a physically meaningful autoionization threshold; please rephrase and clarify the interpretation.
  4. [Section II C] The paragraph beginning "Multiconfigurational PECs for CN+/CN/CN- were simulated at varying bond distances..." appears twice with only minor wording differences; please remove the duplicate.
  5. [Section II B and Section II D] Please justify the choice of 0.05 eV HWHM lifetime broadening for the vibronic spectra and 0.4 eV HWHM for the electronic spectra, and specify whether the 0.4 eV includes instrumental broadening or only lifetime effects.

Circularity Check

1 steps flagged · score 6.0 of 10

Absolute 0-0 energies reported as multiconfigurational wavepacket results are set to the BLYP spectrum by construction; only relative vibronic shapes are independently computed, so the abstract's attribution and the cross-method 'validation' of the energy positions are circular.

  1. fitted input called prediction [Abstract; Fig. 4 caption; Sec. III E (Vibronic fine structures)]
    "Abstract: 'We further calculated the vibronic fine structures for these transitions using the quantum wavepacket method based on multiconfigurational-level, anharmonic potential energy curves, revealing distinct energy positions for the 0-0 absorptions at 280.7 eV, 279.6 eV, and 285.8 eV.' Fig. 4 caption: 'For clarity in fine structure comparisons, all other methods were aligned to the BLYP spectrum by adjusting the 0-0 peak.'"

    The multiconfigurational RASSCF/RASPT2 wavepacket curves in Fig. 4 do not determine the quoted 0-0 energies: the caption says their 0-0 peaks were explicitly adjusted to match the BLYP curve. Therefore the agreement among methods on the 0-0 positions, and the abstract's statement that the wavepacket calculation 'revealed' 280.7/279.6/285.8 eV, is true by construction rather than by independent calculation. The only independent information in the multiconfig curves is the relative vibronic shape (0-1/0-2 spacings and intensity ratios). The reported absolute positions are BLYP-FCH values plus the CO+-derived shift, so the multiconfig curves cannot validate those positions, and the paper's claim of cross-method validation of the energy positions is circular by construction.

full rationale

The derivation is otherwise largely self-contained. The method-specific shift δ is determined by aligning CO+ to an external experimental spectrum, not to the target molecules CN+, CN, or CN-; that is a transferability assumption and a source of correctness risk, but it is not circular. Self-citations to the group's codes (MCNOX, XSpecTime) and to their prior method paper [11] are not load-bearing circularity here: [11] is benchmarked against external experimental XPS/XAS data, and the codes implement standard wavepacket/Morse procedures with stated parameters. The one genuine circular step is the Fig. 4 alignment: because all non-BLYP curves are shifted so their 0-0 peaks coincide with BLYP, the agreement in absolute peak position is imposed, not discovered. The abstract's phrasing makes the wavepacket/multiconfigurational calculation appear to be the source of the 0-0 energies, whereas those energies are predetermined by the BLYP spectrum. Because the electronic assignments (C1s→σ* vs C1s→π*) and the relative vibronic profiles remain independently computed, the circularity is partial rather than total, but it directly affects the headline quantitative claim of three distinct 0-0 positions.

Assumptions & free parameters 2 free parameters · 5 assumptions · 0 invented entities

The paper introduces no new physical entities. Predictions rest on standard electronic-structure methods, one fitted calibration shift per method, and modeling assumptions about active spaces, potential energy surfaces, and transferability of the calibration.

free parameters (2)
  • Method-specific ad hoc energy shift δ = Values from Fig. 2 (approx. -0.39, -1.75, -0.01, -1.75 eV for BLYP, RASSCF/MOLPRO, RASSCF/MOLCAS, RASPT2/MOLCAS)
    Shift aligning the computed CO+ first peak to experiment; assumed transferable to all target species. Directly sets the absolute 0-0 energies.
  • Spectral broadening HWHM = 0.4 eV (electronic spectra); 0.05 eV (vibronic lifetime)
    Chosen linewidths matching instrumental and lifetime broadening. Affects spectral shape and intensity ratios but not peak positions.
assumptions (5)
  • domain assumption The full core hole approximation and the chosen active spaces accurately describe the C1s core-excited states; state averaging over 30 core-excited states (5 for PECs) is sufficient.
    Invoked in Section II B; if the active space or number of states is insufficient, peak positions and intensities would change.
  • domain assumption The ad hoc shift δ obtained for CO+ is transferable to the carbon-nitrogen species with different charge states.
    Section II B; load-bearing for absolute energies; no direct evidence provided for transferability across charge states.
  • domain assumption The Morse potential form adequately represents the anharmonic PECs over the sampled bond-length range.
    Section II C, Eq. (3); all PECs are fitted to Morse potentials; systematic deviations would alter vibronic intensities.
  • domain assumption The sudden approximation for core excitation and the wavepacket propagation parameters (time step 1 a.u., duration 6x10^6 a.u.) yield converged vibronic spectra.
    Section II D; standard for X-ray absorption; assumes no significant nuclear dynamics beyond the propagated wavepacket and converged propagation.
  • domain assumption Ground-state geometries from BLYP-DFT are adequate references for vertical XAS calculations.
    Section II A; all spectra are computed at BLYP-optimized geometries; sensitivity to the geometry choice is not tested.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Predicting Accurate X-ray Absorption Spectra for CN$^+$, CN, and CN$^-$: Insights from Multiconfigurational and Density Functional Simulations." pith.science (2026). https://pith.science/paper/CBJFBLS4

@misc{pith2026241219065,
  author       = {Pith},
  title        = {Pith review of: Predicting Accurate X-ray Absorption Spectra for CN$^+$, CN, and CN$^-$: Insights from Multiconfigurational and Density Functional Simulations},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/CBJFBLS4}},
  note         = {Machine review of arXiv:2412.19065}
}
abstract

High-resolution X-ray spectroscopy is an essential tool in X-ray astronomy, enabling detailed studies of celestial objects and their physical and chemical properties. However, comprehensive mapping of high-resolution X-ray spectra for even simple interstellar and circumstellar molecules is still lacking. In this study, we conducted systematic quantum chemical simulations to predict the C1s X-ray absorption spectra of CN$^+$, CN, and CN$^-$. Our findings provide valuable references for both X-ray astronomy and laboratory studies. We assigned the first electronic peak of CN$^+$ and CN to C1s $\rightarrow \sigma^*$ transitions, while the peak for CN$^-$ corresponds to a C1s $\rightarrow \pi^*$ transition. We explained that the two-fold degeneracy ($\pi^*_{xz}$ and $\pi^*_{yz}$) of the C1s$\rightarrow\pi^*$ transitions results in CN$^-$ exhibiting a significantly stronger first absorption compared to the other two systems. We further calculated the vibronic fine structures for these transitions using the quantum wavepacket method based on multiconfigurational-level, anharmonic potential energy curves, revealing distinct energy positions for the 0-0 absorptions at 280.7 eV, 279.6 eV, and 285.8 eV. Each vibronic profile features a prominent 0-0 peak, showing overall similarity but differing intensity ratios of the 0-0 and 0-1 peaks. Notably, introducing a C1s core hole leads to shortened C-N bond lengths and increased vibrational frequencies across all species. These findings enhance our understanding of the electronic structures and X-ray spectra of carbon-nitrogen species, emphasizing the influence of charge state on X-ray absorptions.

Figures

Figures reproduced from arXiv: 2412.19065 by the authors.

Figure 1
Figure 1. FIG. 1: Energy level diagram of (a) CO [PITH_FULL_IMAGE:figures/full_fig_p010_1.png] view at source ↗
Figure 2
Figure 2. FIG. 2: Simulated C1s XAS spectra for CO, CO [PITH_FULL_IMAGE:figures/full_fig_p011_2.png] view at source ↗
Figure 3
Figure 3. FIG. 3: Simulated PECs for the ground (bottom) and the lowest C1s [PITH_FULL_IMAGE:figures/full_fig_p012_3.png] view at source ↗
Figures from the paper (2 more)
Figure 4
Figure 4. Figure 4: FIG. 4: Vibrationally-resolved C1s XAS spectra for the lowest C1s e [PITH_FULL_IMAGE:figures/full_fig_p012_4.png]
Figure 5
Figure 5. Figure 5: FIG. 5: Overlay of vibrationally-resolved C1s XAS spectra for the lo [PITH_FULL_IMAGE:figures/full_fig_p013_5.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

77 extracted references · 76 canonical work pages

  1. [1]

    Carravetta, R

    V. Carravetta, R. C. Couto, and H. ˚ Agren, X-ray absorp- tion of molecular cations—a new challenge for electronic structure theory, J. Phys.: Condens. Matter 34, 363002 (2022)

    work page 2022

  2. [2]

    Ueda, High-resolution inner-shell spectroscopies o f free atoms and molecules using soft-x-ray beamlines at the third-generation synchrotron radiation sources, J

    K. Ueda, High-resolution inner-shell spectroscopies o f free atoms and molecules using soft-x-ray beamlines at the third-generation synchrotron radiation sources, J. Phys. B: At. Mol. Opt. Phys. 36, R1 (2003)

    work page 2003

  3. [3]

    Hergenhahn, Vibrational structure in inner shell photoionization of molecules, J

    U. Hergenhahn, Vibrational structure in inner shell photoionization of molecules, J. Phys. B: At. Mol. Opt. Phys. 37, R89 (2004)

    work page 2004

  4. [4]

    Svensson, Soft x-ray photoionization of atoms and molecules, J

    S. Svensson, Soft x-ray photoionization of atoms and molecules, J. Phys. B: At. Mol. Opt. Phys. 38, S821 (2005)

    work page 2005

  5. [5]

    Bambi and J

    C. Bambi and J. Jiang, High-Resolution X-ray Spec- troscopy: Instrumentation, Data Analysis, and Science (Springer Nature, 2023)

    work page 2023

  6. [6]

    Y. Ezoe, T. Ohashi, and K. Mitsuda, High-resolution x- ray spectroscopy of astrophysical plasmas with x-ray mi- crocalorimeters, Rev. Mod. Plasma Phys. 5, 1 (2021)

    work page 2021

  7. [7]

    Mosnier, E

    J.-P. Mosnier, E. T. Kennedy, P. van Kampen, D. Cubaynes, S. Guilbaud, N. Sisourat, A. Puglisi, S. Carniato, and J.-M. Bizau, Inner-shell photoex- citations as probes of the molecular ions CH + , OH+ , and SiH + : Measurements and theory, Phys. Rev. A 93, 061401(R) (2016)

    work page 2016

  8. [8]

    Lindblad, L

    R. Lindblad, L. Kjellsson, R. Couto, M. Timm, C. B¨ ulow, V. Zamudio-Bayer, M. Lundberg, B. von Issendorff, J. Lau, S. Sorensen, V. Carravetta, H. ˚ Agren, and J.-E. Rubensson, X-ray absorption spectrum of the N + 2 molec- ular ion, Phys. Rev. Lett. 124, 203001 (2020)

    work page 2020

Show all 77 references
  1. [9]

    R. C. Couto, W. Hua, R. Lindblad, L. Kjellsson, S. L. Sorensen, M. Kubin, C. B¨ ulow, M. Timm, V. Zamudio- Bayer, B. Von Issendorff, J. S¨ oderstr¨ om, J. T. Lau, J.- E. Rubensson, H. ˚ Agren, and V. Carravetta, Breaking inversion symmetry by protonation: experimental and theor...

    2021

  2. [10]

    Carniato, J.-M

    S. Carniato, J.-M. Bizau, D. Cubaynes, E. T. Kennedy, S. Guilbaud, E. Sokell, B. McLaughlin, and J.-P. Mosnier, Vibrationally and Spin-Orbit-Resolved Inner- Shell X-ray Absorption Spectroscopy of the NH + Molec- ular Ion: Measurements and ab Initio Calculations, Atoms 8, 67 (2020)

    2020

  3. [11]

    Zhang, M

    L. Zhang, M. Wei, G. Ge, and W. Hua, Franck- Condon simulation of vibrationally resolved x-ray spec- tra for diatomic systems: Validation of the har- monic approximation and density functional theory, Phys. Rev. A 109, 032815 (2024)

    2024

  4. [12]

    Siegbahn, ESCA applied to free molecules (North- Holland Publishing, 1969)

    K. Siegbahn, ESCA applied to free molecules (North- Holland Publishing, 1969)

    1969

  5. [13]

    Ehara, H

    M. Ehara, H. Nakatsuji, M. Matsumoto, T. Hata- moto, X.-J. Liu, T. Lischke, G. Pr¨ umper, T. Tanaka, C. Makochekanwa, M. Hoshino, et al. , Symmetry- dependent vibrational excitation in N 1s photoioniza- tion of N 2: Experiment and theory, J. Chem. Phys. 124 (2006)

    2006

  6. [14]

    P¨ uttner, I

    R. P¨ uttner, I. Dominguez, T. Morgan, C. Cisneros, R. Fink, E. Rotenberg, T. Warwick, M. Domke, G. Kaindl, and A. Schlachter, Vibrationally resolved O 1 s core-excitation spectra of CO and NO, Phys. Rev. A 59, 3415 (1999)

    1999

  7. [15]

    R. C. Couto, L. Kjellsson, H. ˚ Agren, V. Carravetta, S. L. Sorensen, M. Kubin, C. B¨ ulow, M. Timm, V. Zamudio- Bayer, B. Von Issendorff, et al. , The carbon and oxygen k-edge nexafs spectra of CO+, Phys. Chem. Chem. Phys. 22, 16215 (2020)

    2020

  8. [16]

    Lindblad, L

    R. Lindblad, L. Kjellsson, E. De Santis, V. Zamudio- Bayer, B. Von Issendorff, S. L. Sorensen, J. T. Lau, W. Hua, V. Carravetta, J.-E. Rubensson, et al. , Experi- mental and theoretical near-edge x-ray-absorption fine- structure studies of NO +, Phys. Rev. A 106, 042814 (2022)

    2022

  9. [17]

    Schippers, P.-M

    S. Schippers, P.-M. Hillenbrand, A. Perry- Sassmannshausen, T. Buhr, S. Fuchs, S. Reinwardt, F. Trinter, A. M¨ uller, and M. Martins, Vibrationally resolved inner-shell photoexcitation of the molecular anion C − 2 , ChemPhysChem 24, e202300061 (2023)

    2023

  10. [18]

    Hua, MCNOX: A code for computing and interpreting ultrafast nonlinear X-ray spectra of molecules at the multiconfigurational level, Comput

    W. Hua, MCNOX: A code for computing and interpreting ultrafast nonlinear X-ray spectra of molecules at the multiconfigurational level, Comput. Phys. Commun. 296, 109016 (2024)

    2024

  11. [19]

    Zhang, W

    Y. Zhang, W. Hua, K. Bennett, and S. Mukamel, Nonlin- ear Spectroscopy of Core and Valence Excitations Using Short X-Ray Pulses: Simulation Challenges, Top. Curr. Chem. 368, 273 (2016)

    2016

  12. [20]

    P. S. Bagus, C. Sousa, and F. Illas, Consequences of electron correlation for XPS binding energies: Rep- resentative case for C(1s) and O(1s) XPS of CO, J. Chem. Phys. 145, 144303 (2016)

    2016

  13. [21]

    Takahashi and L

    O. Takahashi and L. G. M. Pettersson, Func- tional dependence of core-excitation energies, J. Chem. Phys. 121, 10339 (2004)

    2004

  14. [22]

    Du, S.-Y

    X. Du, S.-Y. Wang, M. Wei, J.-R. Zhang, G. Ge, and W. Hua, A theoretical library of N1s core binding ener- gies of polynitrogen molecules and ions in the gas phase, Phys. Chem. Chem. Phys. 24, 8196 (2022)

    2022

  15. [23]

    McKellar, Evidence for the Molecular Origin of Some Hitherto Unidentified Interstellar Lines, Publ

    A. McKellar, Evidence for the Molecular Origin of Some Hitherto Unidentified Interstellar Lines, Publ. Astron. Soc. Pac. 52, 187 (1940)

    1940

  16. [24]

    E. J. Bakker, L. Waters, H. J. Lamers, N. R. Trams, and F. L. Van der Wolf, Detection of C 2, CN, and NaID absorption in the AGB remnant of HD56126, Astron. As- trophys. (1995)

    1995

  17. [25]

    G. I. Boger and A. Sternberg, CN and HCN in Dense Interstellar Clouds, Astrophys. J. 632, 302 (2005)

    2005

  18. [26]

    L. E. Snyder, Cometary Molecules, Symposium-IAU 150, 427 (1992)

    1992

  19. [27]

    B. D. Savage and K. R. Sembach, Interstel- lar Abundances from Absorption-Line Obser- vations With the Hubble Space Telescope, Annu. Rev. Astron. Astrophys. 34, 279 (1996)

    1996

  20. [28]

    Dalgarno and R

    A. Dalgarno and R. A. McCray, The Forma- tion of Interstellar Molecules from Negative Ions, Astrophys. J. 181, 95 (1973)

    1973

  21. [29]

    P. J. Sarre, On the possible detection of negative ions i n the interstellar medium., J. Chim. Phys. 77, 769 (1980)

    1980

  22. [30]

    C. A. Gottlieb, S. Br¨ unken, M. C. McCarthy, and P. Thaddeus, The rotational spectrum of CN − , J. Chem. Phys. 126, 191101 (2007)

    2007

  23. [31]

    hollow anode

    T. Amano, Extended negative glow and “hollow anode” discharges for submillimeter-wave observation of CN − , 8 C2H− , and C 4H− , J. Chem. Phys. 129, 244305 (2008)

    2008

  24. [32]

    Ag´ undez, J

    M. Ag´ undez, J. Cernicharo, M. Gu´ elin, C. Kahane, E. Roueff, J. K/suppress los, F. J. Aoiz, F. Lique, N. Marcelino, J. R. Goicoechea, M. G. Garc´ ıa, C. A. Gottlieb, M. C. McCarthy, and P. Thaddeus, Astronomical identifica- tion of CN − , the smallest observed molecular anion...

    2010

  25. [33]

    A. G. G. M. Tielens, The molecular universe, Rev. Mod. Phys. 85, 1021 (2013)

    2013

  26. [34]

    L. E. Snyder and D. Buhl, Observations of radio emission from interstellar hydrogen cyanide, Astrophys. J. 163, L47 (1971)

    1971

  27. [35]

    Schilke, C

    P. Schilke, C. Comito, and S. Thorwirth, First detectio n of vibrationally excited HNC in space, Astrophys. J.582, L101 (2003)

    2003

  28. [36]

    Anderson and L

    J. Anderson and L. Ziurys, Detection of CCN (X 2Πr) in IRC+10216: Constraining carbon-chain chemistry, As- trophys. J. Lett. 795, L1 (2014)

    2014

  29. [37]

    L. Zack, D. Halfen, and L. Ziurys, Detection of FeCN (X4∆i) in IRC+10216: a new interstellar molecule, As- trophys. J. Lett. 733, L36 (2011)

    2011

  30. [38]

    L. M. Ziurys, The chemistry in circumstellar envelopes of evolved stars: Following the origin of the elements to the origin of life, Proc. Natl. Acad. Sci. 103, 12274 (2006)

    2006

  31. [39]

    Gu´ elin, S

    M. Gu´ elin, S. Muller, J. Cernicharo, A. Apponi, M. Mc- Carthy, C. Gottlieb, and P. Thaddeus, Astronomical de- tection of the free radical SiCN, Astron. Astrophys. 363, L9 (2000)

    2000

  32. [40]

    Gu´ elin, S

    M. Gu´ elin, S. Muller, J. Cernicharo, M. McCarthy, and P. Thaddeus, Detection of the SiNC radical in IRC+10216, Astron. Astrophys. 426, L49 (2004)

    2004

  33. [41]

    Ohishi, D

    M. Ohishi, D. McGonagle, W. M. Irvine, S. Yamamoto, and S. Saito, Detection of a new interstellar molecule, H2CN, Astrophys. J. 427, L51 (1994)

    1994

  34. [42]

    Smith, Formation and destruction of molecular ions in interstellar clouds, Philos

    D. Smith, Formation and destruction of molecular ions in interstellar clouds, Philos. Trans. Royal Soc. A 324, 257 (1988)

    1988

  35. [43]

    Ag´ undez, N

    M. Ag´ undez, N. Marcelino, and J. Cernicharo, Discov- ery of interstellar isocyanogen CNCN: Further evidence that dicyanopolyynes are abundant in space, Astrophys. J. Lett. 861, L22 (2018)

    2018

  36. [44]

    A. J. Remijan, J. M. Hollis, F. J. Lovas, D. F. Plusquel- lic, and P. Jewell, Interstellar isomers: The importance of bonding energy differences, Astrophys. J. 632, 333 (2005)

    2005

  37. [45]

    P. ˚ A. Malmqvist, A. Rendell, and B. O. Roos, The re- stricted active space self-consistent-field method, imple - mented with a split graph unitary group approach, J. Phys. Chem. 94, 5477 (1990)

    1990

  38. [46]

    M. G. Delcey, T. B. Pedersen, F. Aquilante, and R. Lindh, Analytical gradients of the state-average com- plete active space self-consistent field method with den- sity fitting, J. Chem. Phys. 143, 044110 (2015)

    2015

  39. [47]

    St˚ alring, A

    J. St˚ alring, A. Bernhardsson, and R. Lindh, Analytical gradients of a state average MCSCF state and a state average diagnostic, Mol. Phys. 99, 103 (2001)

    2001

  40. [48]

    Finley, P.- ˚ A

    J. Finley, P.- ˚ A. Malmqvist, B. O. Roos, and L. Serrano-Andr´ es, The multi-state CASPT2 method, Chem. Phys. Lett. 288, 299 (1998)

    1998

  41. [49]

    A. A. Granovsky, Extended multi-configuration quasi- degenerate perturbation theory: The new approach to multi-state multi-reference perturbation theory, J. Chem. Phys. 134, 214113 (2011)

    2011

  42. [50]

    C. Lee, W. Yang, and R. G. Parr, Develop- ment of the Colle-Salvetti correlation-energy for- mula into a functional of the electron density, Phys. Rev. B 37, 785 (1988)

    1988

  43. [51]

    A. D. Becke, Density-functional exchange-energy approximation with correct asymptotic behavior, Phys. Rev. A 38, 3098 (1988)

    1988

  44. [52]

    M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S. Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S. Su, T. L. Win- dus, M. Dupuis, and J. A. Montgomery, General atomic and molecular electronic structure system, J. Comput. Chem. 14, 1347 (1993)

    1993

  45. [53]

    M. S. Gordon and M. W. Schmidt, Advances in electronic structure theory: Gamess a decade later, in TACC (El- sevier, 2005) pp. 1167–1189

    2005

  46. [54]

    Kutzelnigg, U

    W. Kutzelnigg, U. Fleischer, and M. Schindler, The IGLO-Method: Ab-initio Calculation and Interpretation of NMR Chemical Shifts and Magnetic Susceptibilities, in Deuterium and Shift Calculation , Vol. 23 (Springer Berlin Heidelberg, Berlin, Heidelberg, 1990) pp. 165–262

    1990

  47. [55]

    R. A. Kendall, T. H. Dunning, Jr., and R. J. Har- rison, Electron affinities of the first-row atoms re- visited. Systematic basis sets and wave functions, J. Chem. Phys. 96, 6796 (1992)

    1992

  48. [56]

    T. H. Dunning, Jr., Gaussian basis sets for use in corre- lated molecular calculations. I. The atoms boron through neon and hydrogen, J. Chem. Phys. 90, 1007 (1989)

    1989

  49. [57]

    Triguero, L

    L. Triguero, L. G. M. Pettersson, and H. ˚ Agren, Calculations of near-edge x-ray-absorption spectra of gas-phase and chemisorbed molecules by means of density-functional and transition-potential theory, Phys. Rev. B 58, 8097 (1998)

    1998

  50. [58]

    W. Hua, K. Bennett, Y. Zhang, Y. Luo, and S. Mukamel, Study of double core hole excitations in molecules by X-ray double-quantum-coherence signals: a multi- configuration simulation, Chem. Sci. 7, 5922 (2016)

    2016

  51. [59]

    W. Hua, S. Mukamel, and Y. Luo, Transient X-ray Ab- sorption Spectral Fingerprints of the S 1 Dark State in Uracil, J. Phys. Chem. Lett. 10, 7172 (2019)

    2019

  52. [60]

    R. V. Pinjari, M. G. Delcey, M. Guo, M. Odelius, and M. Lundberg, Cost and sensitivity of restricted active- space calculations of metal L-edge X-ray absorption spec- tra, J. Comput. Chem. 37, 10.1002/jcc.24237 (2016)

    2016 doi

  53. [61]

    R. H. Temperton, N. W. Rosemann, M. Guo, N. Johans- son, L. A. Fredin, O. Prakash, K. W¨ arnmark, K. Han- drup, J. Uhlig, J. Schnadt, and P. Persson, Site-selective orbital interactions in an ultrathin iron-carbene photo- sensitizer film, J. Chem. Phys. A 124, 1603 (2020), pub-...

    2020

  54. [62]

    M. G. Delcey, R. Lindblad, M. Timm, C. B¨ ulow, V. Zamudio-Bayer, B. v. Issendorff, J. Tobias Lau, and M. Lundberg, Soft X-ray signatures of cationic man- ganese–oxo systems, including a high-spin manganese(V) complex, Phys. Chem. Chem. Phys. 24, 3598 (2022), publisher: Royal S...

    2022

  55. [63]

    W. Hua, S. Oesterling, J. D. Biggs, Y. Zhang, H. Ando, R. de Vivie-Riedle, B. P. Fingerhut, and S. Mukamel, Monitoring conical intersections in the ring opening of fu- ran by attosecond stimulated X-ray Raman spectroscopy, Struct. Dyn. 3, 023601 (2016)

    2016

  56. [64]

    Werner, P

    H.-J. Werner, P. J. Knowles, G. Knizia, F. R. Manby, and M. Sch¨ utz, Molpro: a general- purpose quantum chemistry program package, 9 Wiley Interdiscip. Rev.: Comput. Mol. Sci. 2, 242 (2012)

    2012

  57. [65]

    W. Hua, Y. Luo, and S. Mukamel, Multi-Configurational methods for ultrafast NOlinear x-ray spectra (MCNOX), version 1.0, http://jszy.njust.edu.cn/lxy/hwj en/list.psp (2019)

    2019

  58. [66]

    Li Manni, I

    G. Li Manni, I. Fdez. Galv´ an, A. Alavi, F. Aleotti, F. Aquilante, J. Autschbach, D. Avagliano, A. Ba- iardi, J. J. Bao, S. Battaglia, L. Birnoschi, A. Blanco- Gonz´ alez, S. I. Bokarev, R. Broer, R. Cacciari, P. B. Calio, R. K. Carlson, R. Carvalho Couto, L. Cerd´ an, L. F. ...

    2023

  59. [67]

    I. Fdez. Galv´ an, M. Vacher, A. Alavi, C. Angeli, F. Aquilante, J. Autschbach, J. J. Bao, S. I. Bokarev, N. A. Bogdanov, R. K. Carlson, L. F. Chibotaru, J. Creutzberg, N. Dattani, M. G. Delcey, S. S. Dong, A. Dreuw, L. Freitag, L. M. Frutos, L. Gagliardi, F. Gen- dron, A. Giu...

    2019

  60. [68]

    Aquilante, J

    F. Aquilante, J. Autschbach, A. Baiardi, S. Battaglia, V. A. Borin, L. F. Chibotaru, I. Conti, L. De Vico, M. Delcey, I. Fdez. Galv´ an, N. Ferr´ e, L. Freitag, M. Garavelli, X. Gong, S. Knecht, E. D. Larsson, R. Lindh, M. Lundberg, P. ˚ A. Malmqvist, A. Nenov, J. Norell, M. O...

    2020

  61. [69]

    P. ˚ A. Malmqvist and B. O. Roos, The casscf state inter- action method, Chem. Phys. Lett. 155, 189 (1989)

    1989

  62. [70]

    P. ˚ A. Malmqvist, B. O. Roos, and B. Schimmelpfennig, The restricted active space (RAS) state interaction ap- proach with spin–orbit coupling, Chem. Phys. Lett. 357, 230 (2002)

    2002

  63. [71]

    P. M. Morse, Diatomic Molecules According to the Wave Mechanics. II. Vibrational Levels, Phys. Rev. 34, 57 (1929)

    1929

  64. [72]

    J. Li, S. Wang, L. Zhang, G. Ge, M. Wei, J. Zuo, and W. Hua, (2024), see Supplemental Material at [URL will be inserted by publisher] for raw data of the PECs used in Fig. 3 and two figures illustrating the effects of the basis set and MO isovalue

    2024

  65. [73]

    Hua and M

    W. Hua and M. Wei, XSpecTime, version 0.9 (2023), Nanjing University of Science and Technology: Nanjing, 2023

    2023

  66. [74]

    W. Hua, G. Tian, and Y. Luo, Theoretical as- sessment of vibrationally resolved C1s X-ray photoelectron spectra of simple cyclic molecules, Phys. Chem. Chem. Phys. 22, 20014 (2020)

    2020

  67. [75]

    G. Tian, S. Duan, W. Hua, and Y. Luo, DynaVib, version 1.0 (2012), Royal Institute of Technology: Sweden, 2012

    2012

  68. [76]

    R. L. Martin, Natural transition orbitals, J. Chem. Phys. 118, 4775 (2003)

    2003

  69. [77]

    P. ˚ A. Malmqvist and V. Veryazov, The binatural orbitals of electronic transitions, Mol. Phys. 110, 2455 (2012). 10 α 1 1 -3.45 11 -3.88 10 -4.99 2 3 4 5 7 8 9 10 12 -3.45 11 -3.63 10 -4.78 3 4 5 6 7 8 9 10 11 12 CN+ Energy/eV 12/13 1.79 11 1.67 10 0.87 4 5 8 CN- CN 12/13 6.6...

    2012

Pith tools

Reviewed August 11, 2026 · model on record in the stance chip above.