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Example: penning ionization

Penning ionization proceeds at a collision between a metastable atom and a ground state or excited atom

A* + B -> A + B+ + e                                                            (1)

Therefore in this process the energy (or a part of that) of the metastabe atom A* is spent to the ionization of the atom B. This process plays an important role in the balance of charged particles and metastable atoms in gas discharge plasmas and plasma devices. As examples of such systems can be mentioned the active media of some gaseous lasers and luminescence lighting lamps, plasma of MHD generators etc.

At a laboratory temperature (T < 1 eV) the process (1) proceeds effectively if the excitation potential of a metastable A* exceeds the ionization potential of atom B. Under this condition the cross section of the process (1) is calculated within the frame of the adiabatic perturbation theory, in accordance with which the interaction between the colliding atoms promotes the transition of a weekly bound electron into the continuum. The calculation consists in the evaluation of a dependence of a probability of such a transition (width of the relevant term of the quasi-molecule) on the inter-nuclear distance, which is performed within the frame of the perturbation theory. The accuracy of calculation is determined by the uncertainty of determination of the width. Fig. 1 compares the velocity and collision energy dependence of the cross section of Penning ionization at collision between the metastable atom Ne(3P0) and ground state atom Ar(310) calculated by KINTECH Lab and measured in [1].

Fig. 1. Velocity and collision energy dependence of the cross section of Penning ionization at collision between the metastable atom Ne(3P0) and ground state atom Ar(310) calculated by KINTECH (solid line) and measured in [1] (dots)

[1]. Tang S.Y, Marcus A.B., Muschlitz E.E. J. Chem. Phys. 56 566 (1972)

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