Ionization: A hole in an inner shell (here: K shell) is generated
by an incident high-energy electron that loses the corresponding
energy E transferred to the ejected electron.*
2. Auger-electron emission: The
hole in the K shell is filled by an electron from an outer shell
(here: L2). The superfluous energy is transferred to
another electron which is subsequently ejected (here: from the L3 level) as Auger electron.
Auger electrons have an energy in the range of some 100 eV to
a few KeV, they are strongly absorbed by the specimen. Consequently,
only Auger electron from the surface can be measured, making
Auger spectroscopy a surface method.