Hard X-ray imaging allow detailed information to be gathered from below the surface of a material through either full-field imaging, where the whole sample is illuminated, or through scanning, where the beam is focused to a small spot which is scanned across the sample. The high intensity and energy of synchrotron X-rays makes it possible to image a much larger range of materials and sample thicknesses than conventional X-ray sources, and the brilliance of the synchrotron source produces very high resolution images.
Often called Non-crystalline diffraction (NCD), Small Angle X-ray Scattering provides essential information on the structure and dynamics of large molecular assemblies in low ordered environments. These are characteristic of living organisms and many complex materials such as polymers and colloids. Small angle scattering covers the angular range up to 1° while WAXS typically covers 5 - 60°. Anomalous SAXS (ASAXS) takes advantage of the tuneable nature of synchrotron X-rays, using X-rays with energies close to the absorption edges of the element under study. This provides information on the specific composition and density fluctuation of the sample.
X-ray tomography is the construction of a three dimensional image from two dimensional projections taken at different orientations (usually with phase contrast or absorption contrast imaging). The tuneability of synchrotron X-rays make it possible to provide increased contrast images, and the coherent nature and high intensity of synchrotron X-rays have led to significant developments in this field, particularly in phase tomography which in the past has required extremely complex instrumentation.
A range of X-ray absorption spectroscopy (XAS) techniques are available at Diamond; including X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), resonant inelastic X-ray scattering (RIXS) and X-ray emission spectroscopy (XES).
Diffraction and scattering techniques analyse the patterns produced when a sample is illuminated by X-rays and causes deflections. Diffraction patterns provide the atomic structure of molecules such as powders, small molecules or larger ordered molecules like protein crystals.
Powder diffraction is used to examine small, weakly interacting crystals in random orientations. Many materials exist as powders or in polycrystalline form, including ceramics, metals, superconductor oxides, pharmaceuticals, geochemicals, zeolites and related porous solids, all of which can be studied with powder diffraction. The technique can be used to study polycrystalline materials such as metals and alloys.
Small molecule diffraction is the most widely used technique for obtaining full three-dimensional structural information of solid-state crystalline materials. This allows characterisation of, for example, molecular packing, guests in a framework structure, the nature of intra- and intermolecular interactions, molecular conformation and static and dynamic disorder. Environmental cells can be used to probe materials under a range of non-ambient conditions.
Diamond Light Source is the UK's national synchrotron science facility, located at the Harwell Science and Innovation Campus in Oxfordshire.
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