Theory of ultrafast processes with X-ray light

Welcome to the website of the DESY group Theoretical Ultrafast X-ray Science (FS-TUXS). We are studying fundamental interactions of ultrashort high-intensity pulses from x-ray free-electron lasers (XFELs) with matter. Our research is tailored to ultimately develop novel nonlinear x-ray spectroscopic and imaging techniques to probe electronic and nuclear degrees of freedom. One focus of our research group is directed towards the understanding of stimulated x-ray emission processes. We explore the amplification x-ray radiation on electronic transitions involving inner electronic shells as novel x-ray sources for the creation of transform-limited sub-femtosecond x-ray pulses (superfluorescence in the x-ray spectral regime) and for developing ultrabright x-ray optical feed-back lasers. We study parametric nonlinear optical x-ray processes in crystals to measure optical response functions on microscopic scales.