Electron-ion collisions

The Boltzmann equation works reasonably well when electrons collide mainly with neutral species. Electron-electron or electron-ion collisions involve coulombic interactions that have a longer range than that of electron-neutral species interactions. Coulombic-interaction potentials vary inversely with separation, but electron-neutral species interaction potentials vary inversely with the fifth or sixth power of separation. 

Photoionization of neutral atoms and molecules and electron-ion collisions, for example, are rich in infinite Rydberg series of Feshbach resonances. On the other hand, only a finite number of Feshbach (and possibly shape) resonances occur in electron-neutral collisions and photodetachment of an electron attached to a neutral species, with an exception of the following cases. 

In fact, this mechanism has been confirmed by a calculation of the cross sections for impact ionization and impact excitation in electron-ion collisions [36]. The latter was found to be exceptionally low for neon. The basic features of recollision excitation follow from an amplitude such as (4.1) with, however, integration over one additional time the first electron tunnels out at the time t", recollides, promotes the bound electron into an excited state with energy Eq2 > E02, and leaves the interaction region at the time t > t", while the bound electron only becomes free at the later time t > t. Figure 4.5 exhibits the results of such a model. Indeed, for a sufficiently high-lying excited state, the region around zero ion momentum is filled in. 

The first amplitude in the integrand of the second term of (10.50) is a half-on-shell element of the time-reversed distorted-wave T matrix T+ for the electron—ion collision (6.87). The approximation calculated for... 

The plasma-oriented approach is also useful in estimating the interaction area between fast and slow charge carriers, by an appropriate adaptation of the concept of collision cross sections to electrolytes. As an illustration, the apparent cross-section radius of 181 nm in the case of a 0.005-mol dm solution subjected to a 1 mT magnetic field compares favorably with the 134 nm computed from the classical Rosenbluth formula applying to electron-ion collisions. 

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