Ultrafast Fourier transform inelastic x-ray scattering

Over the past few years, x-ray free-electron lasers (FELs) have demonstrated the possibility for probing materials with femtosecond time resolution and Angstrom spatial sensitivity. Here, we review a novel development of Fourier transform inelastic x-ray scattering (FT-IXS), which exploits the ultrafast pulses from an FEL to capture frozen snapshots of the lattice vibrations at multiple length scales simultaneously, as they oscillate when excited by a short laser pulse. This article includes an overview of the principle behind this method and a review of recent work that uses this technique to access microscopic, wave vector-dependent information on how electrons couple to the lattice and to capture phonon–phonon scattering events in real time.