Accurate detn. of the transient electronic structures, which drive photochem. reactions, is crucial in chem. and biol. The authors report the detection of transient chem. changes on the picosecond time scale by x-ray-absorption near-edge structure of photoexcited aq. [Ru(bpy)3]2+. Upon ultrashort laser pulse excitation a charge transfer excited state having a 300 ns lifetime is formed. The authors detect the change of oxidn. state of the central Ru atom at its L3 and L2 edges, at a temporal resoln. of 100 ps with the zero of time unambiguously detd. [on SciFinder (R)]