After an inner shell excitation an atom has an energy above its ground state. It can relax and lose some of this energy in several ways, of which two are described here. Both start with an outer electron jumping in to fill the vacancy in the inner shell.

Characteristic X-ray emission. Energy is given off as a single X-ray photon.

Auger electron emission. Energy is given off by one of the outer electrons leaving. It carries a characteristic kinetic energy.

These two alternative processes are simulated opposite.

Following a K shell excitation, why are the energies of the emitted characteristic X-ray and the equivalent emitted Auger electron slightly different?