X-ray Absorption Spectroscopy (XAS)

X-ray Absorption Spectroscopy (XAS) is a technique to analyze the elemental properties of a material. It can also allow one to understand the chemistry on a molecular level and whether the material is amorphous or crystalline.  XAS has dignificant advantages compared to other methods since it is element specific, no high vacuum required, and no specific sample preparation is required. The XAS experiments can be either static (before and/or after reactions) or dynamic (in situ reactions) while the materials can be in solid, liquid, or gaseous states.

Photo: Photoabsortioncoefficient of Pb showing K, L, and M edges

XAS of Pb showing K, L, and M edges. The shaded yellow energy range is accessible at CAMD

Beamlines for XAS

LEXAS (low energy: between 1.0 and 4.5 keV)

DCM (between 1.7 and 11 keV)

HEXAS (high energy: between 4.5 and 30 keV)

VLSPGM (0.2 – 1.2 keV)

Typical crystals at LEXAS or DCM are InSb(111) for Si, P, S, and Ca - for HEXAS are Ge220, Ge422, Ge531 and the VLSPGM is a ruled diffraction grating. 

Applications

XAS is a technique with many application.  Examples of research conductted at CAMD include: