Extended X-ray absorption fine structure

X-ray Absorption Spectroscopy (XAS) includes both Extended X-Ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES). XAS is the measurement of the x-ray absorption coefficient ( in the equations below) of a material as a function of energy. X-rays of a narrow energy resolution are shone on the sample and the incident and transmitted x-ray intensity is recorded as the incident x-ray energy is incremented. The number of x-ray photons that are transmitted through a sample (I_t) is equal to the number of x-ray photons shown on the sample (I₀) multiplied by a decreasing exponential that depends on the type of atoms in the sample, the absorption coefficient , and the thickness of the sample .