Ultrafast x-ray absorption probing of a chemical reaction

Ultrafast x-ray techniques can, in principle, allow us to more directly watch the time evolution of matter, with atomic spatial resolution and with time resolution on the scale of atomic motions such as the making and breaking of chemical bonds, in order to more directly observe the fundamental molecular dynamics underlying the concept of ‘‘mechanism’’ in inorganic, organic, and biochemical reactions. As a step toward this goal, we have observed a chemical reaction process, photoinduced dissociation of gas phase SF6 molecules, detected by ultrafast near-edge x-ray absorption spectroscopy with time resolutions of 1.5–3 ps, near the sulfur K edge at a photon energy of 2.48 keV (4.98 A).