Time-resolved XAS (Bonn-SUT-SLRI) beamline at SLRI.

An energy-dispersive X-ray absorption spectroscopy beamline has been constructed at the Synchrotron Light Research Institute, Thailand. The beamline was designed to utilize the synchrotron radiation with photon energies between 2400 and 8000 eV. The horizontal focusing of the bent crystal in the energy-dispersive monochromator offers a small polychromatic focal spot of 1 mm at the sample position. By employing an energy-dispersive scheme, the whole X-ray absorption near-edge structure (XANES) can be obtained simultaneously using a position-sensitive detector with a fastest readout speed of 25 ms. The short data collection time opens a new opportunity for time-resolved X-ray absorption spectroscopy (XAS) experiments such as studies of changes of the electronic structures or the local coordination environments of an atom during a change in thermodynamic conditions. For this purpose, an in situ cell was designed and fabricated for the beamline. Thermal oxidation of TiO(2) was chosen as an in situ experiment example. The structural change of TiO(2) as a function of temperatures was monitored from the change in the measured XAS spectra. The obtained Ti K-edge XANES spectra clearly show the formation of an anatase phase when the temperature was raised to 673 K.