Probing in “real-time” the structural evolution of crystals, molecules or proteins in the course of a phase transition, a reaction or a (bio)chemical function has been and still is one of the main goals of modern science.
We attack these problems using both optical domain ultra-fast spectroscopy, and time-resolved X-ray spectroscopy. A powerful tool for the optical experiments is our fluorescence upconversion setup, which enables us to obtain UV/vis emission spectra with 100 fs time-resolution.
Time-resolved optical spectroscopy can provide valuable information on the relevant time scales; however, it can hardly reveal a full picture of structural rearrangements in complex systems. Ultrafast X-ray and electron diffraction techniques are successfully applied to a wide variety of systems, and can already provide movies of physical processes at the atomic resolutions of time (femtoseconds to picoseconds) and space (sub-Angströms). However, as most of chemistry and biology occur in liquids, it is desirable to have a technique that can probe light-induced ultrafast electronic and structure changes of molecular systems in solution. Our approach is based on picosecond (ps) and femtosecond (fs) X-ray absorption spectroscopy (XAS).