Time-dependent Density Functional Theory Simulation of Ultrafast X-ray Spectroscopy Signals Enabled by XFEL

Because of its atomic pinpoint accuracy and high sensitivity to the local electronic structure, X-ray spectroscopy has great advantage over infrared or optical spectroscopy to detect ultrafast chemical dynamics. Thanks to the development of intense X-ray laser technology, now nonlinear spectroscopy techniques has been extended to the X-ray regime. However, accurately simulating modern X-ray spectroscopy still poses a great challenge to theoretical chemists. A new computational protocol for simulating stimulated X-ray Raman spectroscopy (SXRS) has been proposed. Numerical evidences show that time-domain SXRS signals serve as excellent tools in detecting electron transfer and excitation energy transfer dynamics, which are of essential importance in renewable energy technology and biomimetic catalyst design. Along with the further development of XFEL (X-ray free-electron laser) technology, theoretical simulations would shed light to the ultrafast evolution of quantum states in important complex systems.