On the method of calibration of the energy dispersive EXAFS beamline at Indus-2 and fitting theoretical model to the EXAFS spectrum

A procedure for calibration of the recently developed energy dispersive EXAFS beamline at the Indus-2 synchrotron source at RRCAT, Indore, India has been described. The procedure involves recording of absorption spectra of two standard samples, whose absorption edge energies are well-established. Two methods have been considered for calibration. In the first method, the position of the first maximum of the derivative of absorption curve is taken as the position of the edge energy. In the second method, the position of the point at half edge step in the absorption curve is taken as the position of the edge energy. It has been shown that only the first method gives same values of dispersion even when the beam current is varied and should be used for calibrating the experimental spectra. Further, it is recommended that the performance of the beamline for a particular setting should be checked by recording and analysing EXAFS of a standard. Hence, the procedure for analysis and extracting information about the various parameters that can be determined by fitting the EXAFS data with a theoretical model has also been described, by taking the example of K-absorption spectra of copper metal foil recorded on this beamline.