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.Penning, F. M. Die Naturwissenschaften, 1927, 15, 818. Über Ionisation durch metastabile Atome.

Reactions

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:

<math>G^* + M to M^ + e^- + G</math>

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:

<math>G^* + M to MG^ + e^-</math>

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

<math>G^* + S to G + S + e^-</math>

(The positive charge symbol <math>S^+</math> 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.)

See......

Read More