title: Observing photochemical transients by ultrafast x-ray absorption spectroscopy.
abstract: Accurate determination of the transient electronic structures, which drive photochemical reactions, is crucial in chemistry and biology. We report the detection of transient chemical changes on the picosecond time scale by x-ray-absorption near-edge structure of photoexcited aqueous [Ru(bpy)(3)](2+). Upon ultrashort laser pulse excitation a charge transfer excited state having a 300 ns lifetime is formed. We detect the change of oxidation state of the central Ru atom at its L3 and L2 edges, at a temporal resolution of 100 ps with the zero of time unambiguously determined.
authors.affiliation: Institut de Physique de la Matière Condensée, Université de Lausanne, BSP, CH-1015 Lausanne, Switzerland.
authors.forename: Melanie
authors.initials: M
authors.lastname: Saes
authors.forename: Christian
authors.initials: C
authors.lastname: Bressler
authors.forename: Rafael
authors.initials: R
authors.lastname: Abela
authors.forename: Daniel
authors.initials: D
authors.lastname: Grolimund
authors.forename: Steven L
authors.initials: SL
authors.lastname: Johnson
authors.forename: Philip A
authors.initials: PA
authors.lastname: Heimann
authors.forename: Majed
authors.initials: M
authors.lastname: Chergui