Experimental Techniques available at CAMD for Material Research
One of the advantages of synchrotron radiation emitted from the CAMD electron-storage ring is the availability of a continuous, wide energy range of photons from infrared to hard X-rays, allowing various experimental techniques to be applied to materials science. The techniques that are currently available at CAMD are described here. The acronyms are defined at the bottom of this page.
Each element has its own specific electronic energy levels and they absorb X-rays (XAS) at energies characteristic of those levels. Near the absorption edge, the spectra may contain fine structure (XANES) that reveals the electronic and geometrical environment of the absorbing atom. Further from the edge the spectra (EXAFS) reveals the local atomic environment to the element.
This is a part of X-ray absorption spectroscopy, generally, for elements with absorption edges located below 1,000 eV. The spectrum is often called as the near edge X-ray absorption fine structure (NEXAFS). Carbon K-edge, nitrogen K-edge, oxygen K-edge, and transient metals L-edges are some of the typical NEXAFS.
X-ray Diffraction (XRD)
X-ray diffraction (XRD) patterns provide interference patterns that allow one to evaluate the atomic structure of crystalline materials, powders, small molecules or larger ordered molecules like protein crystals.
This technique provides structural information on and dynamics of large molecular assemblies in non-crystalline materials. Many complex materials such as polymers and colloids, and living organisms can be investigated.
The atomic and molecular structure of protein crystals can be investigated by X-ray diffraction which is able to determining the three-dimensional structure of large biological molecules, proteins and enzymes.
Microtomography is similar to a medical CAT scan but with about 1000 times better spatial resolution, and with synchrotron radiation it can be elementally sensitive. It is accomplished by imaging by sections and reconstructing a 3D model of the object under analysis. It can be used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, and other sciences.
Ultra-violet absorption spectroscopy of gas samples can be performed, providing information on electronic structure. In addition, UV and VUV photo irradiation effects on materials can be studied.
The energy of photoelectrons emitted from a sample are analyzed, and depending on the energy of the synchrotron light they can provide information on the electronic band structure (UPS), they can be made as a function of emission angle (ARPES) or provide information on elemental oxidation states (XPS).
The determination of functional groups in organic and inorganic molecules can be performed by measuring transmission or reflection of IR energy. Special optics allows position-sensitive imaging of specimens. This method has broad applications in biology, chemistry, archaeology and environmental analyses.
XAS = X-ray Absorption Spectroscopy
XANES = X-ray Absorption Near-Edge Spectroscopy
EXAFS = Extended X-ray Absorption Fine Structure
NEXAFS = Near Edge X-ray Absorption Fine Structure
WAXS = Wide Angle X-Ray Scattering
GISAXS = Grazing-Incidence Small-Angle Scattering
UV = Ultra-Violet
UPS = Ultraviolet Photoelectron Spectroscopy
ARPES = Angle-Resolved Photoelectron Spectroscopy
XPS = X-ray Photoelectron Spectroscopy
IR = Infra-Red