Exploiting EXAFS and XANES for time-resolved molecular structures in liquids

A review. Time-resolved X-ray absorption fine structure (XAFS) spectroscopy with picosecond temporal resoln. is a new method to observe electronic and geometric structures of short-lived reaction intermediates. It combines an intense femtosecond laser source synchronized to the X-ray pulses delivered by a synchrotron light source (SLS). We present key expts. on charge transfer reactions as well as spin-crossover processes in coordination chem. compds. next to solvation dynamics studies of photogenerated at. radicals. These examples emphasize the observables at hand using ultrafast XAFS techniques, which include the d. of states, full and even partial changes in oxidn. state, and internuclear distances with milli-Angstrom accuracy. An outlook towards femtosecond studies and biol. relevant systems stresses the high potential of XAFS methods using new femtosecond X-ray sources like free electron lasers (XFELs).