Time-resolved imaging using x-ray free electron lasers

Abstract

The ultra-intense, ultra-short X-ray pulses provided by X-ray Free Electron Laser (XFEL) sources are ideally suited to time resolved studies of structural dynamics with spatial resolution from nanometre to atomic length scales and temporal resolution of 10 fs or less. Using coherent X-ray diffraction as a diagnostic, XFELs enable the capturing of X-ray snapshots of previously unmeasurable transient phenomena, and the study of ultrafast processes such as sample damage on the timescales which they occur. With enough photons in a single pulse to enable single-shot measurements, and short enough pulses to freeze atomic motion, researchers now have a new window into the time evolution ultrafast phenomena that are intrinsically not cyclic in nature. In this review paper we recap some of the key time-resolved imaging experiments performed at FLASH and look ahead to a new generation of experiments at higher resolution using a new generation of new XFEL sources that are only just becoming available.

Advanced x-ray multilayer waveguide optics

“…The present work is entirely focused on continuous-wave (cw) illumination (both simulation and experiment), one could also explore the effect of such RBCs on ultra-short and focused x-ray pulses, as generated by free-electron laser (FEL) or higher harmonic (HHG) radiation. In particular, such designed multi-guide resonant beam couplers could serve as time-delay beam splitters with attosecond delay, orders of magnitude smaller than current macroscopic pulse delay stages [90,91]. Multi-guide RBCs in combination with sub-µm beams, may further be useful to probe surface and near-surface structure and dynamics.…”

“…The Goos-Hänchen effect observed for focused x-ray beams under resonant-mode-excitation pulse delay stages [90,91]. Multi-guide RBCs in combination with sub-µm beams may further be useful to probe surface and near-surface structure and dynamics.…”

Multidimensional scattering of attosecond x-ray pulses detected by photon-coincidence

“…Under these conditions the field-matter interaction Hamiltonian is given by equation (5). Such experiments have been proposed as a means of taking stroboscopic images of systems in nonequilibrium states and thus tracking the system's evolution [23][24][25][26]. The use of temporally well-separated pulses reflects the experimental goal of taking 'pictures' of the system at distinct points in time and creating a stop-motion style recording and, furthermore, greatly simplifies the resulting expressions.…”

Dynamics of colloidal crystals studied by pump-probe experiments at FLASH

“…At the same time, newly developed free-electron lasers (FEL) [17][18][19][20] are especially well suited for time-resolved experiments on ultrafast structural dynamics of different materials, 21 including colloids. FELs provide extremely powerful coherent femtosecond x-ray pulses, which are necessary to perform time-resolved experiments with a time resolution that outperforms that of third-generation synchrotron sources.…”