Why the Core Electrons?

• An electron near the Fermi level is far from the nucleus, moving in different directions all over the place, and will not carry information about any single atom.

• Fermi level is the highest energy level occupied by an electron in a neutral solid at absolute 0 temperature.

• Electron binding energy (BE) is calculated with respect to the Fermi level.

• The core e^-s are local close to the nucleus and have binding energies characteristic of their particular element.

• The core e^- s have a higher probability of matching the energies of AlKα and MgKα .