Penning Ionization

Penning ionization is a form of chemi-ionization, an ionization process involving reactions between neutral atoms and/or molecules. The process is named after the Dutch physicist Frans Michel Penning who first reported it in 1927. The Penning effect is put to practical use in applications such as gas-discharge neon lamps and fluorescent lamps, where the lamp is filled with a Penning mixture to improve the electrical characteristics of the lamps.


Penning ionization refers to the interaction between a gas-phase excited-state atom or molecule G* and a target molecule M resulting in the formation of a radical molecular cation M+., an electron e−, and a neutral gas molecule G:

G* + M -> M+• + e- + G

Penning ionization occurs when the target molecule has an ionization potential lower than the internal energy of the excited-state atom or molecule. Associative Penning ionization can also occur:

G* + M -> MG+• + e-

Surface Penning ionization refers to the interaction of the excited-state gas with a surface S, resulting in the release of an electron.

G* + S -> G + S + e-

(The positive charge symbol ‪S +‬ that would appear to be required for charge conservation is omitted, because S is a macroscopic surface and the loss of one electron has a negligible effect.) Wikipedia, Penning Ionization

See Also

12.32 - Ionization Atomic Cluster Ionization ionization Penning Mixture Sympathetic Resonance Sympathetic Oscillation Sympathetic Vibration

Created by Dale Pond. Last Modification: Sunday February 19, 2012 03:58:26 MST by Dale Pond.