XAFS AND X-MCD SPECTROSCOPIES WITH UNDULATOR GAP SCAN

The first experimental applications of the undulator gap-scan techniqu e in X-ray absorption spectroscopy are reported. The key advantage of this method is that during EXAFS scans the undulator is permanently tu ned to the maximum of its emission peak in order to maximize the photo n statistics. In X-MCD or spin-polarized EXAFS studies with a helical undulator of the Hellos type, the polarization rate can also be kept a lmost constant over a wide energy range.