Penning and Associative Ionization of Atoms

A full analysis, similar to that for two-body radiative combination (Section 3), is difficult because of this steep variation of 1V R). However, because fV R)lh is much larger than radiative transition probabilities, a completely different approach is possible, of which the simplest example is an orbiting model, in which aU collisions surmounting the centrifugal barrier lead to ionization, with the transition restricted solely to the inner turning-point, Rc. By assuming a form for fV(R), the possibility 

This classical model has been extended further by Nakamura and Miller by including interference effects between the incoming and outgoing portions of the trajectory this resulting semiclassical approach is equivalent to a WKB analysis of the quantum mechanical treatment, employing the stationary-phase approximation.  

The orbiting and the classical and semiclassical impact parameter models have been used to interpret inelastic scattering data in chemiionization, the dependence of ionization cross-section on collision energy and electron energy spectra, in order to gain information about the potential curves, V and V, and the autoionization width, (/ ). 

Chemi-ionization of Noble Gas Atoms. The form of the A + A potentials, V, has been studied by elastic scattering, - as discussed in Section 3, and well depths and equilibrium separations are listed in TaUe 11. hi the studies of differential scattering cross-sections, inelastic scattering due to energy transfer or ionization was clearly observable at large angles, the 

In the analysis of such data, the effect of a centrifugal barrier in V must be 

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Penning and Associative Ionization of Atoms.—Several workers have described chemi-ionization reactions of He with an atom, M, in terms of autoionizing transitions between adiabatic potential curves, V and V, correlating with He + M and He + M respectively. Figure 2 shows schematic curves and transitions, representing the processes ... 

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