Two-color X-ray pulses capture the same nanoparticle at two moments in time

One big dream of ultrafast science has been to watch changes in nanoparticles or biomolecules on their natural timescale. Experimentally, this can be realized by taking two snapshots of the same object only femtoseconds apart. However, no detector is fast enough to record the two snapshots separately—they end up on top of each other in a single image.

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