Imaging Molecular Motions in Space and Time: Ultrafast X-Ray Diffraction of Electrocyclic Chemistry at the LCLS

Ultrafast molecular structure transformations, like those found in 1,3-cyclohexadiene (CHD) and 1,4-diiodobenzene (DIB) are prototypical electrocyclic processes that serve as a model for numerous chemical reactions in organic synthesis and natural product biology.  In our initial LCLS experiments we demonstrated that robust x-ray diffraction signals could be obtained for dilute (≤ 30 Torr) gas targets.  Building on this exciting discovery we very recently (< 2 weeks ago) pushed the cutting edge further and confirmed that significant time resolved structural dynamics could be observed at much less than an order of magnitude sample density.  I will describe the technical points of our experimental approach and present our initial groundbreaking results on CHD and DIB.