A laser and synchrotron radiation pump-probe X-ray absorption experiment with sub-ns resolution

We present the concept of an experiment that aims at probing in real-time photoinduced structural modifications in a large class of media ranging from biological systems to solid state materials using time-resolved X-ray spectroscopies (Extended X-ray Absorption Fine Structure-EXAFS or X-ray Absorption Near-Edge Structure-XANES) in the picosecond time domain. The principle of the experiment is based on the pump-probe scheme, where an ultrashort laser pulse induces a structural modification in a chemical, physical or biological system. The picosecond hard X-ray pulse from a synchrotron probes the evolution of the structure in real-time by means of an adjustable time delay between the pump and the probe pulses. The paper discusses the case of iodine in liquid solvents as a test bench of the technique.