Resulting from an Instantaneous Current Pulse

Diffusion Resulting from an Instantaneous Current Pulse 

There is another important diffusion problem, the solution of which can be generated from the concentration response to a constant current (or a flux). Consider that in an eleetroehemieal system there is a plane electrode at the boundary of the eleetrolyte. Now, suppose that with the aid of an electronic pulse generator, an extremely short time eurrent pulse is sent through the system (Fig. 4.28). The current is direeted so as to dissolve the metal of the eleetrode hence, the effect of the pulse is to produee a burst of metal dissolution in whieh a layer of metal ions is piled up at the interface (Fig. 4.29). 

Beeause the eoneentration of metal ions at the interface is far in excess of that in the bulk of the solution, diffusion into the solution begins. Since the source of the diffusing ions is an ion layer parallel to the plane electrode, it is known as a plane source and since the diffusing ions are produced in an instantaneous pulse, a fuller deseription of the souree is eontained in the term instantaneous plane source. 

As the ions from the instantaneous plane source diffuse into the solution, their concentration at various distances will change with time. The problem is to calculate the distance and time variation of this concentration. 

The starting point for this calculation is the general relation between the Laplace transforms of the concentration perturbation c, and the time-varying flux/(t) 

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