DIFFRACTION ANOMALOUS FINE STRUCTURE AT THE ESRF BY USING DISPERSIVE & MONOCHROMATIC DIFFRACTION. J. L. Hodeau^1,2, J. Vacinova¹, H. Renevier¹, P. Wolfers¹, J. F. Berar¹, M. Hagelstein², A. San Miguel², ¹Lab. Cristallographie CNRS, BP 166, F-38042 Grenoble, France, ²ESRF, BP 220, F-38043 Grenoble, France

We present several Diffraction Anomalous Fine Structure (DAFS) studies performed at ESRF and at LURE on platinum or iron oxydes and on multilayers, using two different experimental modes: the Dispersive Diffraction mode (DD) which uses the combination of X-ray energy dispersive optics, sample goniometer and a two dimensional position sensitive detector and the Multi Monochromatic Diffraction mode (MMD) performed with classical monochromatic optics. We discuss our last results obtained at ESRF by using these two experimental modes for DAFS data collection. The DD technique would be precious for time dependent investigations and in-situ experiments and it could be used not only for DAFS experiments but also for other anomalous scattering experiments.

The DAFS spectroscopy provides in the same experiment information regarding the local atomic environment through X-ray absorption processes and long-range order information through diffraction processes. It can provide site selective and chemical selective structural information. Up to now, most results obtained with this method concern materials where structural information can be extracted from pure, site-selective Bragg reflections. Our studies apply the technique to highly absorbing "real" materials and to multilayers containing several anomalous atoms which do not respect the latter restriction. An accurate empirical absorption correction procedure for small highly absorbing single crystals necessary for the DAFS analysis of this kind of samples is developed. We present a simultaneous multi-wavelength refinement procedure of several Bragg reflections with the anomalous terms f' of different crystallographic sites as unknowns.