Practical Aspects at an Electrochemical Interface

As a basis for quantitative analysis of IR data in an ATR geometry, the absorption of a thin layer of absorbing species has been calculated, assuming that this layer, of thickness d, can be described as a medium with a complex dielectric function E(a)=e -ie [24]. The latter may even be taken as anisotropic with principal directions x, y, z (hence e, Sy, Sz) vvhere z is the direction normal to the interface and xz is the incidence plane. The relative changes in IR reflection, calculated to first order in d, are then [24] 

Even though the ATR geometry exhibits a fair immunity to electrolyte absorption, the latter will stiU be orders of magnitude larger than the absorption of interface species, which are typically in a concentration of a monolayer (d/2 A/ 253 1 A). In practice, IR absorption will then be dominated by the electrolyte (see Fig. 6.3). Howevei interface species are expected to be sensitive to a number of parameters, while the electrolyte bulk is not. Such parameters may be the time (spontaneous evolution of the interface under given electrochemical 

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