Cited by 337Laser-Matter Interactions and ApplicationsAdvanced X-ray Imaging TechniquesX-ray Spectroscopy and Fluorescence Analysis

The DOI matches its Crossref record; 226 of the 226 references it cites were found in a registry or an index; 14 of the 230 sources its claims cite were checked for support.

Roadmap of ultrafast x-ray atomic and molecular physics

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Abstract

X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (10 20 W cm −2 ) of x-rays at wavelengths down to ∼1 Ångstrom, and HHG provides unprecedented time resolution (∼50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ∼280 eV (44 Ångstroms) and the bond length in methane of ∼1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This roadmap surveys ultrafast x-ray atomic and molecular physics enabled by XFELs and HHG sources, organizing perspectives from 17 leading groups into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies, high-intensity x-ray phenomena, and attosecond x-ray science. It documents source capabilities, scientific opportunities, and technical challenges as new Ångstrom-wavelength XFEL facilities open and HHG reaches attosecond time resolution.

Key findings

  • XFELs provide unprecedented x-ray intensity of 10^20 W cm^-2 at wavelengths down to ∼1 Ångstrom, while HHG provides time resolution of ∼50 attoseconds and large coherent bandwidth at longer wavelengths.
  • The roadmap frames relevant scales by the hydrogen Bohr orbital period of 150 attoseconds, the hydrogen-molecule vibrational period of 8 femtoseconds, the carbon K-edge at ∼280 eV (44 Ångstroms), and the methane bond length of ∼1 Ångstrom.
  • Three new Ångstrom-wavelength XFEL facilities opened for users around the time of the roadmap—European XFEL, Swiss-FEL, and PAL-FEL in Korea—almost doubling the worldwide number of XFELs.
  • Specific advances cited include attosecond pulses as short as 43 as and 53 as, charge migration across iodoacetylene in less than 1 fs, transient lattice contraction within 80 fs, and emission of more than 50 electrons within a few tens of fs at x-ray intensities exceeding 10^19 W cm^-2.

Methods

  • This is a roadmap/community-perspective article, not a primary experimental study; it captures the perspectives of 17 leading groups and organizes contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies, high-intensity x-ray phenomena, and attosecond x-ray science.
  • The text reviews source capabilities and experimental techniques for XFELs and HHG, including coherent diffractive imaging, nonlinear x-ray processes, multidimensional spectroscopy, photoionization time-delay measurements, and attosecond transient absorption.
  • It discusses current and future challenges and advances needed in sources, instrumentation, theory, and computation, with examples drawn from experiments and simulations across atoms, molecules, clusters, liquids, and solids.

Limitations

  • The paper states that most XFELs are based on self-amplified spontaneous emission (SASE), lack longitudinal coherence, struggle to obtain pulse lengths shorter than a few femtoseconds, and struggle to synchronize with external sources.
  • It states that HHG sources have exquisite temporal coherence and pulse duration but are challenged to obtain large photon numbers per pulse, extend to short wavelengths, and achieve high average power.
  • It notes that low repetition rates at current XFELs limit coincidence measurements, that SASE spectral fluctuations hamper nonlinear x-ray spectroscopy, and that theoretical treatment of high-intensity x-ray-driven polyatomic systems remains a central challenge; the roadmap format itself is not a systematic review or meta-analysis.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1088/1361-6455/aa9735

Cites

226 of 226 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

161 Not checked yet · 137 No basis given · 135 Own interpretation · 5 Partly supported · 5 Own result · 2 Own method · 1 Supported · 1 Supported so far · accuracy not yet measured

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Show all 218 claims

  • It may state two separate claims as one. 133
  • Probably not a substantial claim. 133
229 of 229
  • The paper relies on this without support.

    Most XFELs are based upon self-amplified spontaneous emission (SASE) radiation, lack longitudinal coherence, struggle to obtain pulse lengths shorter than a few femtoseconds and struggle to synchronize with external sources.

    “Most XFELs are based upon self-amplified spontaneous emission (SASE) radiation, lack longitudinal coherence, struggle to obtain pulse lengths shorter than a few femtoseconds and struggle to synchronize with external sources.”
  • The paper relies on this without support.

    HHG sources have exquisite temporal coherence and pulse duration, but are challenged to obtain large photon numbers per pulse, to extend their reach to short wavelengths and to obtain high average power.

    “HHG sources, on the other hand, have exquisite temporal coherence and pulse duration, but are challenged to obtain large photon numbers per pulse, to extend their reach to short wavelengths and to obtain high average power.”
  • The paper relies on this without support.

    XFEL facilities can provide x-ray pulses with durations down to a few femtoseconds.

    “The XFEL facilities can provide x-ray pulses with durations down to a few femtoseconds.”
  • The paper relies on this without support.

    Producing pulses of duration below a femtosecond is technically feasible.

    “Producing pulses of duration below a femtosecond is also technically feasible.”
  • The paper relies on this without support.

    Focused intensities up to 10^20 W cm^-2 or more permit nonlinear studies, and the high peak fluence enables single-shot diffraction based on the principle of 'diffract before destroy.'

    “Focused intensities up to 10 20 W cm -2 or more permit nonlinear studies, and the high peak fluence enables single-shot diffraction based on the principle of 'diffract before destroy.'”
  • The paper relies on this without support.

    Core energy levels are highly element specific.

    “Since core energy levels are highly element specific, this technique can provide structural and dynamical information with high spatial, temporal, and spectral resolutions not feasible with optical pulses.”
  • The authors state this as an assumption.

    Larger chemical shifts than with single core hole states are expected for double core hole states.

    “Double core hole (DCH) states have recently received growing interest, mainly because larger chemical shifts than with single core hole states are expected.”
  • The paper relies on this without support.

    The effect of nuclear wavepacket propagation on the first excited states in a time shorter than one femtosecond plays a crucial role in the ultrafast fragmentation observed.

    “One of the challenges is to control ultrafast fragmentation in the sub-femtosecond time scale; the effect of the nuclear wavepacket propagation on the first excited states in a time shorter than one femtosecond plays a crucial role in the ultrafast fragmentation observed.”
  • The paper relies on this without support.

    The future of research in this field very much depends on optical issues, synchrotron facilities upgrades and technical improvements of end-stations.

    “The future of research in this field very much depends on optical issues, synchrotron facilities upgrades and technical improvements of end-stations.”
  • The paper relies on this without support.

    The probability for fluorescent decay in the soft x-ray range is below 1%.

    “Unfortunately, the probability for fluorescent decay in the soft x-ray range is below 1%, and this represents a challenge for signal detection.”
  • The authors state this as an assumption.

    For interactions with hard x-rays, the electrons in a material can be approximated as quasi-free when the x-ray energy is well above the atomic resonances.

    “For interactions with hard x-rays, the electrons in a material can be approximated as quasi-free when the x-ray energy is well above the atomic resonances.”
  • The authors state this as an assumption.

    Within XMDYN, neutral atoms, atomic ions, and ionized electrons are treated as classical point particles.

    “Within this framework, neutral atoms, atomic ions, and ionized electrons are treated as classical point particles.”
  • The authors state this as an assumption.

    The force between a pair of charged particles is simply Coulombic; the force between two neutral atoms, or between a neutral atom and an atomic ion, is parametrized as in classical force-field calculations.

    “The force between a pair of charged particles is simply Coulombic; the force between two neutral atoms, or between a neutral atom and an atomic ion, is parametrized as in classical force-field calculations.”
  • The authors state this as an assumption.

    The ionization dynamics of the atoms in XMDYN are treated stochastically by using bound-electron-configuration-dependent cross sections and rates computed with XATOM.

    “The ionization dynamics of the atoms are treated stochastically by using bound-electronconfiguration-dependent cross sections and rates computed with XATOM.”
  • The authors state this as an assumption.

    In the small energy region considered in figure 23, both τXUV and τcc are constant and do not affect the measurement of the phase variation.

    “In the small energy region considered in figure 23, both τ XUV and τ cc can be assumed to be constant and do not affect the measurement of the phase variation.”
  • The authors state this as an assumption.

    One of the photoionization delays can be sufficiently accurately calculated to serve as an absolute reference.

    “except if we assume that one of the delays can by sufficiently accurately calculated to serve as an absolute reference [186].”
  • The paper relies on this without support.

    Water is highly transmissive in the water window.

    “because water is highly transmissive in the water window where the absorption edges of carbon (284 eV) and nitrogen (410 eV) lie.”
  • The paper relies on this without support.

    The conversion efficiency obtained at 3.9 μm of ∼5% can be maintained at 500 Hz to reach a 50 mJ class MIR laser based on existing Yb laser technologies.

    “Considering the recent conversion efficiency obtained at 3.9 μm of ∼5%, a 50 mJ class MIR laser at 500 Hz is reachable based on existing Yb laser technologies.”
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Citations

Cites

Show all 226 references

Research works printed but not linked: 6

  1. Larsson M, 2015, 2015 Nobel Symp. Free Electron Laser Res.
  2. 10.1103/PhysRevLett.115.193003 · DOI · Paper page
  3. 10.1038/nature14894 · DOI · Paper page
  4. 10.1126/sciadv.1500837 · DOI · Paper page
  5. 10.1038/ncomms11493 · DOI · Paper page
  6. Ferray M, 1988, J. Phys. B: At. Mol. Opt. Phys., 21, L31, 10.1088/0953-4075/21/3/001 · DOI · Paper page

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Metadata

Authors
Young, L., Ueda, K., Gühr, M., Bucksbaum, P. H., Simon, M., Mukamel, S., Rohringer, N., Prince, K. C., Masciovecchio, C., Meyer, M., Rudenko, A., Rolles, D., Bostedt, C., Fuchs, M., Reis, D. A., Santra, R., Kapteyn, H., Murnane, M., Ibrahim, H., Légaré, F., Vrakking, M., Isinger, M., Kroon, D., Gisselbrecht, M., L’Huillier, A., Wörner, H. J., & Leone, S. R.
Affiliations
  • Argonne National Laboratory (US)
  • Tohoku University (JP)
  • University of Potsdam (DE)
  • SLAC National Accelerator Laboratory (US)
  • Centre National de la Recherche Scientifique (FR)
  • University of California, Irvine (US)
  • Universität Hamburg (DE)
  • Elettra-Sincrotrone Trieste S.C.p.A. (IT)
  • European X-Ray Free-Electron Laser (DE)
  • Kansas State University (US)
  • University of Nebraska–Lincoln (US)
  • Joint Institute for Laboratory Astrophysics (US)
  • Institut National de la Recherche Scientifique (CA)
  • Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy (DE)
  • Lund University (SE)
  • ETH Zurich (CH)
  • University of California, Berkeley (US)
Corresponding author
Young, Linda
Venue
Journal of Physics B: Atomic, Molecular and Optical Physics
Published
2018-01-09
Volume
51
Issue
3
Pages
032003
ISSN
  • 0953-4075 (ISSN-L)
  • 1361-6455
OpenAlex
W2784192443
Cited by
337
References
226
Citations by year
2026: 17 · 2025: 32 · 2024: 40 · 2023: 48 · 2022: 47 · 2021: 53 · 2020: 54 · 2019: 30 · 2018: 16
FWCI
17.68
Type
journal article
Language
en
Open access
Locations
  • Journal of Physics B Atomic Molecular and Optical Physics (publishedVersion, cc-by)
  • K-State Research Exchange (Kansas State University) (submittedVersion, cc-by)
  • OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (submittedVersion, cc-by)
  • Repository for Publications and Research Data (ETH Zurich) (submittedVersion, cc-by)
  • Lincoln (University of Nebraska) (submittedVersion)
  • HAL (submittedVersion, other-oa)
  • DESY Publication Database (PUBDB) (Deutsches Elektronen-Synchrotron) (submittedVersion, other-oa)
  • eScholarship (California Digital Library) (submittedVersion)
  • publish.UP (University of Potsdam) (submittedVersion, cc-by)
  • Lund University Publications (Lund University) (submittedVersion)
  • Refubium (Universitätsbibliothek der Freien Universität Berlin) (submittedVersion, cc-by)
  • European XFEL (submittedVersion, cc-by)
  • Universitätsbibliothek der FU Berlin Hochschulschriftenstelle u. Dokumentenserver (cc-by)
  • ETH Zürich Research Collection (cc-by)
Funders
  • National Science Foundation (0310717, 1125844, 1663822, 1548924)
  • U.S. Department of Energy (FG02-04ER15571, DE‐FG02‐, 76SF00515, DE–AC02–76SF00515, DEFG0204ER15571, AC02‐76SF00515, DEFG0299ER14982, DESC0016494, DE-AC02-)
  • Gordon and Betty Moore Foundation (DE-AC02-76SF00515)
  • University of Chicago
  • Institut national de la recherche scientifique
  • Volkswagen Foundation
  • Ministry of Education, Culture, Sports, Science and Technology
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
  • Eidgenössische Technische Hochschule Zürich
  • Knut och Alice Wallenbergs Stiftelse
  • Vetenskapsrådet
  • Centre National de la Recherche Scientifique
  • Universität Hamburg
  • Université Pierre et Marie Curie
  • Defense Advanced Research Projects Agency (1125844, W31P4Q, W31P4Q-13-1-0015)
  • Office of Science (AC02-76SF00515, DE-AC02-76SF0051 5, DE-AC02, DEFG0204ER15571, 76SF00515)
  • University of California, Irvine
  • Advanced Research Projects Agency
  • Deutsches Elektronen-Synchrotron
  • Division of Materials Research (DMR1548924, 1548924)
  • Division of Chemistry (CHE1663822)
  • Basic Energy Sciences (DE-AC02, DEFG02- 04ER15571, DE-FG02, 76SF00515, FG02-04ER15571, AC02-76SF00515, DE-AC-02-76SF00515)
  • Chemical Sciences, Geosciences, and Biosciences Division (DE-FG02-04ER15571, DE-AC02-76SF00515)
  • Air Force Office of Scientific Research
  • Army Research Office
  • Argonne National Laboratory
  • SLAC National Accelerator Laboratory
Topics
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Laser-Matter Interactions and Applications
  • Physical Sciences › Physics and Astronomy › Radiation › Advanced X-ray Imaging Techniques
  • Physical Sciences › Physics and Astronomy › Radiation › X-ray Spectroscopy and Fluorescence Analysis
Keywords
X-ray free-electron laser, high harmonic generation, coherent diffraction imaging, attosecond photoionization, conical intersections, ultrafast molecular dynamics

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