Development of 100ps Time-resolved XAS and Observation of Spin Crossover Dynamics in Solution

Experimental strategy and setup for the 100 ps time-resolved X-ray absorption spectroscopy (TR-XAS) is presented. X-ray positional active feedback combined with a figure-of-merit scan of the laser beam position was employed as a key technique. It is shown that the pump-probe TR-XAS technique using the X-ray pulse structure of synchrotron radiation sources is a powerful tool to investigate dynamics of the electronic state and molecular structure of non-crystalline samples. A TR-XAS measurement of a photo-induced spin crossover reaction of the tris(1,10-phenanthrorine)iron(II) complex in water is presented.