Researchers measure hard X-ray pulses lasting 170 attoseconds

Researchers demonstrated a method to measure attosecond hard X-ray pulses directly in time, reporting an average pulse duration of 170 attoseconds in Nature. Precise measurement and control of these pulses had limited their use in experiments observing electron motion in matter. The team used an apparatus that splits broadband X-ray pulses and delays them relative to one another. Measurements of correlations between the fields characterized coherence time and demonstrated attosecond synchronization of pulse pairs. A nonlinear probe based on two-photon absorption measured the average pulse duration. The demonstrated tools support experiments using one X-ray pulse to excite a sample and another to probe its response; the duration measurement describes an average across pulses.