Transient-species crystallography at ChemMatCARS
February 2003
In Collaboration with Philip Coppens (SUNY-Buffalo), T. Graber at ChemMatCARS recently performed the first pump-probe time-resolved crystallography experiment at the ChemMatCARS facility. 
Using an x-ray beam chopper developed by the Coppens group, a 355 nm pulsed laser beam (pump) was synchronized with the chopped monochromatic high-brilliance undulator x-ray beam (probe).
By collecting a diffraction pattern immediately after the probe laser pulse from the sample, which is maintained at a temperature close to that of liquid helium, an excited state molecular geometry is extracted using conventional crystallography techniques.
The CCD frame of Cu(dmp)(diphos)PF6 (shown above) shows diffraction spots from the excited state crystal. Many of these frames are collected with different crystal orientations and the set of frames are refined yielding a molecular structure.
The facility is being developed to probe the structure of transient species with lifetimes to a few microseconds.