QEXAFS IN SECONDS AT AN UNDULATOR SOURCE

An experimental setup for QEXAFS, which enables sub-second time resolution, is decribed. The QEXAFS spectrometer was established at the TROIKA beamline at the European Synchrotron Radiation Facility. Time resolved QEXAFS measurements of dynamic processes in catalytic materials at the time scale of seconds were made possible by utilizing the high brilliance of the 2nd harmonic of the undulator spectrum and a multi channel analyser data acquisition system together with the existing single crystal monochromator setup. The minium acquisition time is neither limited by the statistics nor the dead time for read out of the data. Rather, the mechanics of the monochromator setup presently limit the minimum time to obtain high quality data but with minor improvements it should be straightforward to reach the sub-second time resolution of QEXAFS even for full spectra. The possibilities of the present setup have been used to elucidate phase transformations occurring during the reduction of a Cu-based methanol synthesis catalyst.