Krausz, F. & Ivanov, M. Attosecond physics. Rev. Mod. Phys. 81, 163–234 https://doi.org/10.1103/RevModPhys.81.163 (2009).
Corkum, P. B. Plasma perspective on strong field multiphoton ionization. Phys. Rev. Lett. 71, 1994–1997 https://doi.org/10.1103/PhysRevLett.71.1994 (1993).
Hentschel, M. et al. Attosecond metrology. Nature 414, 509–513 https://doi.org/10.1038/35107000 (2001).
Paul, P. M. et al. Observation of a train of attosecond pulses from high harmonic generation. Science 292, 1689–1692 https://doi.org/10.1126/science.1059413 (2001).
Duris, J. et al. Tunable isolated attosecond X-ray pulses with gigawatt peak power from a free-electron laser. Nat. Photon. 14, 30–36 https://doi.org/10.1038/s41566-019-0549-5 (2020).
Huang, Z. & Kim, K.-J. Review of X-ray free-electron laser theory. Phys. Rev. ST Accel. Beams 10, 034801 https://doi.org/10.1103/PhysRevSTAB.10.034801 (2007).
Pellegrini, C., Marinelli, A. & Reiche, S. The physics of X-ray free-electron lasers. Rev. Mod. Phys. 88, 015006 https://doi.org/10.1103/RevModPhys.88.015006 (2016).
Bonifacio, R., De Salvo, L., Pierini, P., Piovella, N. & Pellegrini, C. Spectrum, temporal structure, and fluctuations in a high-gain free-electron laser starting from noise. Phys. Rev. Lett. 73, 70–73 https://doi.org/10.1103/PhysRevLett.73.70 (1994).
Zhang, Z. et al. Experimental demonstration of enhanced self-amplified spontaneous emission by photocathode temporal shaping and self-compression in a magnetic wiggler. New J. Phys. 22, 083030 https://doi.org/10.1088/1367-2630/aba14c (2020).
Prat, E. et al. Coherent sub-femtosecond soft X-ray free-electron laser pulses with nonlinear compression. APL Photonics 8, 111302 https://doi.org/10.1063/5.0164666 (2023).
Li, S. et al. “Beam à la carte”: laser heater shaping for attosecond pulses in a multiplexed X-ray free-electron laser. Appl. Phys. Lett. 125, 191101 https://doi.org/10.1063/5.0233468 (2024).
Franz, P. et al. Terawatt-scale attosecond X-ray pulses from a cascaded superradiant free-electron laser. Nat. Photon. 18, 698–703 https://doi.org/10.1038/s41566-024-01427-w (2024).
Guo, Z. et al. Experimental demonstration of attosecond pump–probe spectroscopy with an X-ray free-electron laser. Nat. Photon. 18, 691–697 https://doi.org/10.1038/s41566-024-01419-w (2024).
Duris, J. P. et al. Controllable X-ray pulse trains from enhanced self-amplified spontaneous emission. Phys. Rev. Lett. 126, 104802 https://doi.org/10.1103/PhysRevLett.126.104802 (2021).
Robles, R. R. et al. Spectrotemporal shaping of attosecond X-ray pulses with a fresh-slice free-electron laser. Phys. Rev. Lett. 134, 115001 https://doi.org/10.1103/PhysRevLett.134.115001 (2025).
O’Neal, J. T. et al. Electronic population transfer via impulsive stimulated X-ray Raman scattering with attosecond soft-X-ray pulses. Phys. Rev. Lett. 125, 073203 https://doi.org/10.1103/PhysRevLett.125.073203 (2020).
Driver, T. et al. Attosecond delays in X-ray molecular ionization. Nature 632, 762–767 https://doi.org/10.1038/s41586-024-07771-9 (2024).
Alexander, O. et al. Attosecond impulsive stimulated X-ray Raman scattering in liquid water. Sci. Adv. 10, 0841 https://doi.org/10.1126/sciadv.adp0841 (2024).
Li, S. et al. Attosecond-pump attosecond-probe X-ray spectroscopy of liquid water. Science 383, 1118 https://doi.org/10.1126/science.adn6059 (2024).
Funke, L. et al. Capturing nonlinear electron dynamics with fully characterised attosecond X-ray pulses. Preprint at 10.48550/arXiv.2408.03858 (2024).
Marinelli, A. et al. Experimental demonstration of a single-spike hard-X-ray free-electron laser starting from noise. Appl. Phys. Lett. 111, 151101 https://doi.org/10.1063/1.4990716 (2017).
Huang, S. et al. Generating single-spike hard X-ray pulses with nonlinear bunch compression in free-electron lasers. Phys. Rev. Lett. 119, 154801 https://doi.org/10.1103/PhysRevLett.119.154801 (2017).
Malyzhenkov, A. et al. Single-and two-color attosecond hard X-ray free-electron laser pulses with nonlinear compression. Phys. Rev. Res. 2, 042018 https://doi.org/10.1103/PhysRevResearch.2.042018 (2020).
Yan, J. et al. Terawatt-attosecond hard X-ray free-electron laser at high repetition rate. Nat. Photon. 18, 1293–1298 https://doi.org/10.1038/s41566-024-01566-0 (2024).
Hartmann, N. et al. Attosecond time–energy structure of X-ray free-electron laser pulses. Nat. Photon. 12, 215–220 https://doi.org/10.1038/s41566-018-0107-6 (2018).
Li, S. et al. Characterizing isolated attosecond pulses with angular streaking. Opt. Express 26, 4531–4547 https://doi.org/10.1364/OE.26.004531 (2018).
Inubushi, Y. et al. Determination of the pulse duration of an X-ray free electron laser using highly resolved single-shot spectra. Phys. Rev. Lett. 109, 144801 https://doi.org/10.1103/PhysRevLett.109.144801 (2012).
Behrens, C. et al. Few-femtosecond time-resolved measurements of X-ray free-electron lasers. Nat. Commun. 5, 3762 https://doi.org/10.1038/ncomms4762 (2014).
Krejcik, P. et al. Sub-fs resolution with the enhanced operation of the X-band transverse deflecting cavity using an RF pulse compression SLED cavity. In Proc. 5th International Beam Instrumentation Conference (IBIC’16) (eds Costa, I. et al.) WEPG77 https://doi.org/10.18429/JACoW-IBIC2016-WEPG77 (JACoW, 2017).
Dicke, R. H. Coherence in spontaneous radiation processes. Phys. Rev. 93, 99 https://doi.org/10.1103/PhysRev.93.99 (1954).
Gross, M. & Haroche, S. Superradiance: an essay on the theory of collective spontaneous emission. Phys. Rep. 93, 301–396 https://doi.org/10.1016/0370-1573(82)90102-8 (1982).
Rohringer, N. & London, R. Atomic inner-shell X-ray laser pumped by an X-ray free-electron laser. Phys. Rev. A 80, 013809 https://doi.org/10.1103/PhysRevA.80.013809 (2009).
Rohringer, N. et al. Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser. Nature 481, 488–491 https://doi.org/10.1038/nature10721 (2012).
Yoneda, H. et al. Atomic inner-shell laser at 1.5-ångström wavelength pumped by an X-ray free-electron laser. Nature 524, 446–449 https://doi.org/10.1038/nature14894 (2015).
Kroll, T. et al. Stimulated X-ray emission spectroscopy in transition metal complexes. Phys. Rev. Lett. 120, 133203 https://doi.org/10.1103/PhysRevLett.120.133203 (2018).
Doyle, M. D. et al. Seeded stimulated X-ray emission at 5.9 kev. Optica 10, 513–519 https://doi.org/10.1364/OPTICA.485989 (2023).
Linker, T. M. et al. Attosecond inner-shell lasing at ångström wavelengths. Nature 642, 934–940 https://doi.org/10.1038/s41586-025-09105-9 (2025).
Chuchurka, S., Benediktovitch, A., Krusic, S., Halavanau, A. & Rohringer, N. Stochastic modeling of X-ray superfluorescence. Phys. Rev. A 109, 033725 https://doi.org/10.1103/PhysRevA.109.033725 (2024).
Chuchurka, S., Sukharnikov, V. & Rohringer, N. Hermitian stochastic methodology for X-ray superfluorescence. Phys. Rev. A 109, 063705 https://doi.org/10.1103/PhysRevA.109.063705 (2024).
Emma, P. et al. First lasing and operation of an ångstrom-wavelength free-electron laser. Nat. Photon. 4, 641–647 https://doi.org/10.1038/nphoton.2010.176 (2010).
Chollet, M. et al. The X-ray pump–probe instrument at the Linac Coherent Light Source. J. Synchrotron Radiat. 22, 503–507 https://doi.org/10.1107/S1600577515005135 (2015).
Inoue, I. et al. Nanofocused attosecond hard X-ray free-electron laser with intensity exceeding 1019 W/cm2. Optica 12, 309–310 https://doi.org/10.1364/OPTICA.554954 (2025).
Kato, M. et al. Pulse energy measurement at the hard X-ray laser in Japan. Appl. Phys. Lett. 101, 023503 https://doi.org/10.1063/1.4733354 (2012).
Zhu, D. et al. A single-shot transmissive spectrometer for hard X-ray free electron lasers. App. Phys. Lett. 101, 034103 https://doi.org/10.1063/1.4736725 (2012).
Inoue, I. et al. Atomic-scale visualization of ultrafast bond breaking in X-ray-excited diamond. Phys. Rev. Lett. 126, 117403 https://doi.org/10.1103/PhysRevLett.126.117403 (2021).
Inoue, I. et al. Femtosecond reduction of atomic scattering factors triggered by intense X-ray pulse. Phys. Rev. Lett. 131, 163201 https://doi.org/10.1103/PhysRevLett.131.163201 (2023).
Mozzanica, A. et al. The JUNGFRAU detector for applications at synchrotron light sources and XFELs. Synchrotron Radiat. News 31, 16–20 https://doi.org/10.1080/08940886.2018.1528429 (2018).
Halavanau, A. et al. Population inversion X-ray laser oscillator. Proc. Natl Acad. Sci. USA 117, 15511–15516 https://doi.org/10.1073/pnas.2005360117 (2020).
Jurek, Z., Son, S.-K., Ziaja, B. & Santra, R. XMDYN and XATOM: versatile simulation tools for quantitative modeling of X-ray free-electron laser induced dynamics of matter. J. Appl. Cryst. 49, 1048 https://doi.org/10.1107/S1600576716006014 (2016).
Campbell, J. L. & Papp, T. Widths of the atomic K–N7 levels. At. Data Nucl. Data Tables 77, 1–56 https://doi.org/10.1006/adnd.2000.0848 (2001).
Chapman, H. N. et al. Femtosecond X-ray protein nanocrystallography. Nature 470, 73–77 https://doi.org/10.1038/nature09750 (2011).
Inoue, I. et al. Observation of femtosecond X-ray interactions with matter using an X-ray–X-ray pump–probe scheme. Proc. Natl Acad. Sci. USA 113, 1492–1497 https://doi.org/10.1073/pnas.1516426113 (2016).
Inoue, I. et al. Delayed onset and directionality of X-ray-induced atomic displacements observed on subatomic length scales. Phys. Rev. Lett. 128, 223203 https://doi.org/10.1103/PhysRevLett.128.223203 (2022).
Ziaja, B., London, R. A. & Hajdu, J. Unified model of secondary electron cascades in diamond. J. Appl. Phys. 97, 064905 https://doi.org/10.1063/1.1853494 (2005).
Robles, R. et al. Broadband hard X-ray attosecond pulses from extremely chirped electron beams. Phys. Rev. Res. 8, 033350 https://doi.org/10.1103/2w1p-jvp1 (2026).
Flöttmann, K. ASTRA: A Space Charge Tracking Algorithm. User manual (DESY, 2023).
Borland, M. Elegant: A Flexible SDDS-Compliant Code for Accelerator Simulation. Report No. ANL/APS/LS-287 (Argonne National Laboratory, 2000).
Wang, Y. & Borland, M. Pelegant: a parallel accelerator simulation code for electron generation and tracking. In Proc. AIP Conference Proceedings 241–247 (American Institute of Physics, 2006).
Reiche, S. Genesis 1.3: a fully 3D time-dependent FEL simulation code. Nucl. Instrum. Methods Phys. Res. A 429, 243–248 (1999).
Reiche, S. Genesis-1.3-Version4. GitHub https://github.com/svenreiche/Genesis-1.3-Version4 (2022).
Ersoy, O. K. Diffraction, Fourier optics and imaging. In Diffraction, Fourier Optics and Imaging 1–5 https://doi.org/10.1002/9780470085004.ch1 (John Wiley & Sons, 2007).