Binding energy of the photoelectron

Figure 4.6. Photoemission and the Auger process. Left An incident X-ray photon is absorbed and a photoelectron emitted. Measurement of its kinetic energy allows one to calculate the binding energy of the photoelectron. The atom becomes an unstable ion with a hole in one of the core levels. Right The excited ion relaxes by filling the core hole...

Eb is the binding energy of the photoelectron with respect to the Fermi level of the sample... 

Equation (3.1) indicates that XPS is capable of elemental analysis since no two atoms in the Periodic Table exhibit the same set of BEs . An XPS spectrum is a plot of the photoelectron intensity versus the kinetic (or binding) energy of the photoelectrons. Qualitative analysis can easily be performed by wide scans, in which all the available KE range is explored. Higher spectral resolution and more quantitative analysis are performed by detailed or narrow KE (or BE) scans. 

The chemical information implicit in the X-ray-in-duced photoelectron spectrum is a very important feature of the XPS technique and is, as mentioned above, the source of the alternative acronym ESCA. For almost all elements the binding energy of the photoelectron peak shows small perturbations that reflect the chemical environment of the element under consideration. 

Binding energies of the photoelectron peaks measured in the contact areas (mean value for all loads), the non-contact areas and for the reference compounds. The standard deviation is 0.1 eV for all values listed,... 

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