Difração Múltipla

In the multiple diffraction phenomenon, in turn, a single X-rays incident beam simultaneously produces more than one diffracted beam in a variety of directions. The X-rays multiple diffraction (XRMD) is interesting because of its high sensitivity – it allows the detection of small distortions in the crystal lattice of the material. Also provides information on the three-dimensional networks, including on the possible interfaces between two distinct materials or between two regions with different crystal structures by using a special multiple diffraction case – the Bragg-Surface Diffraction (BSD). Thus, the method is able to extract structural information simultaneously from two or more crystalline regions within the samples, which usually is not available from other conventional techniques.

It is interesting to note that the information can be obtained both in the sample surface and the interfaces between different parts of it, when present. For example, one can determine the phase of the analyzed structure, allowing to distinguish between a structure and its “image” in the mirror. This important information is lost in the most traditional diffraction techniques.

The main part of the experimental group activities is performed on XRD1 beamline the National Synchrotron Light Source (LNLS) in Campinas, which was adapted to the XRMD experiments. The reason is that the LNLS synchrotron radiation provides polarized X-rays on one plane, with high intensity, very low divergence and tuning the appropriate wavelength – conditions which, when taken simultaneously, allow for unique experiences with this technique. Furthermore, it is possible to change the polarization of the incidence plane in XRD1 beamline, which has turned out to be very important for some of the experiments with XRMD.