Molecular movie in femtosecond time scale

A team led by Dr. M. Minitti (SLAC National Accelerator Laboratory, USA) has recently succeeded in recording the time evolution of a structural change of ring-type 1,3-cyclohexadiene gas molecule to linear 1,3,5-hexatriene. The employment of the X-ray free-electron laser at LCLS (Linac coherent light source), Stanford allowed them to do ultra fast snapshots of X-ray scattering in several tens of fs (femtosecond) scale. The study is based on pump-and-probe measurement; i.e., X-ray data were collected as a function of the controlled delay time between the UV pump pulse (267 nm, 65 fs, 4-8 μJ, 100 μm size) and X-ray probe pulse (8.3 keV, around 30 fs, 10¹² photons/pulse, 30 μm square size). The team established that some signals caused by structural change are found as early as 30 fs, and the reaction finishes at 200 fs. For more information, see the paper, "Imaging Molecular Motion: Femtosecond X-Ray Scattering of an Electrocyclic Chemical Reaction", M. P. Minitti et al., Phys. Rev. Lett. 114, 255501 (2015).