Auger effect
Definition and meaning of Auger effect in chemistry.
The Auger effect is a non-radiative atomic process in which an inner-shell electron vacancy is filled by an outer-shell electron, and the released energy is transferred to another electron that is subsequently ejected from the atom.
In more detail
When an atom is ionized and loses an inner-shell electron, an outer-shell electron falls down to fill the vacancy. Rather than the atom emitting this energy as an X-ray photon, the energy can be directly transferred to a second outer-shell electron, which is then ejected. This ejected electron, called an Auger electron, carries kinetic energy characteristic of the specific atom and the electron shells involved. The Auger effect competes with X-ray fluorescence for de-excitation and dominates in lighter elements, while X-ray emission becomes more probable for heavier atoms.
Key facts
| Field | Physical Chemistry |
|---|---|
| Process type | Non-radiative electron transition |
| Key application | Auger electron spectroscopy (AES) |
| Discovered | 1923 by Pierre Auger |
In a carbon atom with a 1s electron vacancy, a 2s electron fills the hole and transfers the released energy to a 2p electron, which is ejected as an Auger electron with characteristic kinetic energy.
Frequently asked questions
How does the Auger effect differ from X-ray fluorescence?
In X-ray fluorescence, excess energy is released as a photon. In the Auger effect, energy transfers directly to another electron which is ejected. Both occur after inner-shell ionization.
Why is Auger electron spectroscopy valuable for surface analysis?
Auger electrons have short mean free paths, so they escape only from the outermost atomic layers, making the technique sensitive to surface composition and chemical environments.