The role of transient resonances for ultra-fast imaging*

Ultrafast imaging with intense short pulses from X-ray free-electron lasers is a promising route to investigate the structure and dynamics of nanoscale systems. The ultrafast imaging process is subject to the sample electronic structure, opening new opportunities to investigate dynamics on the shortest time scales. We have developed a computational approach for describing ultrafast imaging experiments and compare it to benchmark data from succrose clsuters. We find that transient phenomena driven by non-linear x-ray interaction are decisive for ultrafast imaging applications and that transient resonances can be exploited to increase the scattering response and elemental contrast. Our study illuminates the complex interplay of the imaging process with the rapidly changing transient electronic structures in XFEL experiments and shows how computational models allow optimization of the parameters for ultrafast imaging experiments.