Ambipolar diffusion mechanism

If one assumes proton (H ), oxide ion (0 ), conduction electron (e), and electron hole (h) as ionic and electronic charge carriers, hydrogen evolution at the permeating side will obey the ambipolar diffusion mechanism, expressed by Eq. (12.17) [36] ... 

Polymerization Mechanism in Region III. In region III, all the electrons cannot be transported to the anode in a half cycle of the discharge frequency. A possible charge transportation mechanism is an ambipolar diffusion of ion and electron pairs which will cause polymerization. The diffusion of free radicals may also contribute to the polymerization. In our experiment, the contribution of these two mechanisms cannot be distinguished because the ion and electron pairs behave as neutral gases. 

Electron Loss Processes. Ambipolar diffusion to the walls is an important mechanism for loss of electrons from the discharge. It is appropriate to enumerate other electron loss mechanisms and then balance these against the various production mechanisms operative in a sustained discharge. 

In cases where a continuous and coherent layer of oxide film is present, further reaction can proceed only by diffusion of some of the reactants across the film. There are several possible mechanisms for this transport of material. In many solids, the passage of neutral atoms is less likely than the transport of charged particles, ions and electrons. In such cases, called ambipolar diffusion, the concentration gradient is not the only constraint on the system. In addition, and at all times, overall charge neutrality needs to be maintained. 

Easily ionisable elements, such as alkali and alkaline earth metal elements, can alter the emission intensity and may cause an enhancement or a depression. This problem is more serious with DCPs, MIPs, and CMPs, while less important with ICPs. Several mechanisms have been suggested to explain these changes, for example lateral diffusion, changes in thermal conductivity, an altered volatihsation rate, ambipolar diffusion, or shifts in the ionisation equilibrium and the collisional processes. 

In a laboratory plasma the dominating ion destruction mechanism is often not the electron recombination in the plasma but the electron recombination at the wall after ambipolar diffusion. Because of the light mass and high temperature, electrons diffuse in the plasma... 

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