Femtosecond snapshots capture atomic motion in a powdered solid

X-ray diffraction has long been an important tool for deducing crystal structures. The x rays scatter off the crystal's electrons, giving a pattern of diffraction peaks related to the electron density; points of concentrated electron density indicate the nuclear positions. In recent decades time-resolved x-ray diffraction has probed faster and faster structural changes, up to and including atomic movements on the femtosecond time scale.