Status And New Applications Of Time-Resolved X-Ray Absorption Spectroscopy

Time-resolved X-ray absorption spectroscopy is a valuable tool for detailed investigations of fast chemical reactions, thin film deposition phenomena, solid state reactions, phase transformations etc. We will report on latest experimental developments which employ a new monochromator design consisting of a cam driven tilt table for rapid angular oscillations and a fixed-exit channel cut crystal. Using cryogenic cooling, the silicon crystal can cope with the full heat load from third generation undulator sources such as the APS, SPring-8 or the ESRF. Depending on photon flux and sample quality, repetition rates of about 100 Hz can be realized for the XANES range, while the acquisition of full EXAFS spectra with a scan range of typically 1 keV are feasible at a repetition rate of 10 Hz. An excellent data quality can be obtained. Since a fast sequential energy scanning technique is used, the detection of fluorescence radiation or surface sensitive techniques can be applied, and a reference sample can be monitored simultaneously with each measurement to detect even minor edge shifts reliably. Furthermore, XANES microtomography in transmisson and fluorescence becomes feasible using the fast scanning monochromator in combination with refractive X-ray lenses for beam focusing