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Penning ionization

Penning ionization is a form of chemi-ionization, an ionization process involving reactions between neutral atoms and/or molecules.^[1]^[2]^[3] The term 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.

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Reactions

$G^* + M \to M^{+\bullet} + e^- + G$

Associative Penning ionization can occur:

$G^* + M \to MG^{+\bullet} + e^-$

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

$G^* + S \to G + S + e^-$

Penning ionization occurs when the target molecule has an ionization potential lower than the internal energy of the excited-state atom or molecule. The process was first reported by F.M. Penning in 1927.

References

^ Penning, F. M. Die Naturwissenschaften, 1927, 15, 818. Über Ionisation durch metastabile Atome.
^ Arango CA, Shapiro M, Brumer P (2006). "Cold atomic collisions: coherent control of penning and associative ionization". Phys. Rev. Lett. 97 (19): 193202. PMID 17155624.
^ Hiraoka K, Furuya H, Kambara S, Suzuki S, Hashimoto Y, Takamizawa A (2006). "Atmospheric-pressure Penning ionization of aliphatic hydrocarbons". Rapid Commun. Mass Spectrom. 20 (21): 3213-22. doi:10.1002/rcm.2706. PMID 17016831.