High-intensity X-ray pump-monochromatic X-ray probe technique across time zero

This is the authors' abstract. We don't add key points for this paper.

A femtosecond pump–probe technique, capable of probing transient changes in intense X-ray-excited matter with monochromatic X-ray pulses and accessing data for both positive and negative delay times, is proposed. The application of this technique to single-crystal silicon revealed ultrafast X-ray-induced electron excitation occurring on a timescale of 10 fs, along with the delayed onset of atomic disordering relative to the electronic excitation. This technique will pave the way for atom-specific multidimensional spectroscopy and diagnostics of exotic states of matter created by X-ray irradiation with sophisticated probing techniques, such as single-crystal diffraction, inelastic scattering, X-ray Thomson scattering, and absorption spectroscopy.