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Hard X-ray attosecond metrology
Nature
(2026) Cite this article
Sub-ångström spatial resolution combined with attosecond temporal resolution enables direct observation of electron motion in matter1. Attosecond hard X-ray pulses generated at X-ray free-electron laser sources provide the requisite spatiotemporal sensitivity, yet their application has been limited by the absence of precise pulse metrology and control. Here, building on a broadband X-ray split-delay line, we establish metrology of attosecond hard X-ray pulses. Field-correlation measurements provide the first time-domain characterization of the pulse coherence time and demonstrate attosecond synchronization between the generated pulse pairs. By exploiting non-sequential two-photon absorption as a nonlinear probe, intensity autocorrelation quantifies the average pulse duration directly in the time domain to be 170 as. The demonstrated experimental tools and techniques enable systematic attosecond time-resolved experiments, including X-ray pump–X-ray probe spectroscopy and diffraction, and open a pathway to probing electronic phenomena with unprecedented spatial-temporal resolution.
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All data in this study are available from the corresponding author upon request.
Krausz, F. & Ivanov, M. Attosecond physics. Rev. Mod. Phys. 81, 163–234 (2009).
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