Light interacts with matter on incredibly tiny scales of space and time—where electrons move in attoseconds and atomic bonds stretch just a few Å. To manipulate such light-matter interaction processes, researchers shape the light pulses, adjusting their amplitude, polarization and phase. While this method is well-established for visible light, extending it to the XUV spectrum is a new frontier.

In a recent experiment at the FERMI free-electron laser facility in Italy, the team of researchers shaped XUV pulses to control the motion of electrons in helium atoms. They succeeded in coherently manipulating "dressed states" which form when intense light interacts with the atom. By fine-tuning the phase of the XUV pulses, they were able to direct how these transient dressed states evolve. This achievement marks a key step toward controlling quantum processes on ultrafast timescales, paving the way for further advancements in chemistry, physics, and materials science.

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