Augermeit

Augermeit, a shell-hopping atom spirit, knocks out an inner electron, and a second one flies out of the atom.

The Physics

Remove an electron from an atom's innermost K shell and an electron from the L shell drops into the hole. The energy released can leave as an X-ray photon. Or it can pass directly to another electron, which is ejected from the atom with a characteristic energy: an Auger electron. No photon is emitted and reabsorbed. For a KLL transition the Auger electron's energy is roughly the K binding energy minus two L binding energies, which makes it a fingerprint of the element. That is the basis of Auger electron spectroscopy.

E_KLL ≈ E_K − E_L − E_L

• E_KLL: kinetic energy of the ejected Auger electron (eV)
• E_K: binding energy of the K-shell electron (eV)
• E_L: binding energies of the two L-shell electrons involved (eV)

Who discovered it is a matter of historical credit. In papers on beta-ray spectra in Zeitschrift für Physik in 1922 and 1923, Lise Meitner described electrons being ejected from the atom's own shells by its characteristic X-ray energy, and pointed to radiationless transitions as a possible cause. Pierre Auger reported his cloud-chamber observation of the effect in 1923 (Comptes rendus 177, 169) and made it the theme of his thesis. Matsakis, Coster, Laster and Sime proposed renaming it the Auger–Meitner effect (Physics Today 72(9), 10, 2019). Other historians, O. Hardouin Duparc (Int. J. Mater. Res. 100, 1162, 2009) and K. Mahnke (Notes Rec. R. Soc. 76, 107, 2020), argue that the credit has rightly gone to Auger. Both names are now in use.

Honest caveat: The energy formula is an approximation: the binding energies shift when the atom already has a hole, and solids add a work-function correction. The order of events in the art is simplified to one hole and one escape.

On the sticker

Augermeit holds out a glowing violet atom as a single electron streaks away from it. Printed text: AUGERMEIT with the line E ≈ EK − EL − EL. Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.