Diffusion origin

The two major causes of uneven current distribution are diffusion and ohmic resistance. Nonuniformity due to diffusion originates from variations in the effective thickness of the diffusion layer 8 over the electrode surface as shown in Figure 10.13. It is seen that 8 is larger at recesses than at peaks. Thus, if the mass-transport process controls the rate of deposition, the current density at peaks ip is larger than that at recesses since the rate of mass transport by convective diffusion is given by... 

Figure 10.24—Raman diffusion. Origin of emission bands cell geometry Raman spectrum of L-cystine.

Fig. 9. The absorption spectrum of quinoxaline in durene at 4.2°K. The transition to the lower electronic state ( w ) is very sharp, that to the higher state (V77 ) is diffuse. The structure on the diffuse origin of the mr transition is real and very complex In this region there is interference between the two states.

Figure 4.8 Schematic representation of an effective source Q defined by two apertures which collimate the diffuse original source. The analyser then has to accept only the smaller effective source Q placed at a vertical distance ds. From [Ris72], see also Fig. 1.16 where S, and S2 act as apertures to restrict Az, the length of the acceptance source volume.

The equation of monomer diffusion originates from (5.153) in a similar way... 

Diffusion originally described the way in which heat (believed to be a fluid) flowed through a solid. Later the same ideas were applied to describe the way in which a gas would spread out to fill the available volume. In solids, diffusion is the transport of atoms, ions or molecules under the influence of a driving force that is usually a concentration gradient. Diffusion takes place in solids at a much slower rate than in gases or liquids and, in the main, it is a high-temperature process. However, this is not always so, and in some solids the rate of diffusion at room temperature is considerable. 

If a diffusible, originally tightly limited system, e.g. a volume of gas,... 

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