Three-Phase System and Linear Approximation

In optical studies of electrode surfaces, we have to consider three phases (1) the bulk electrolyte, (2) the interfacial region, and (3) the bulk electrode 

FIGURE 8. Angular dependence of the electric field strength for p-polarized light at a gold surface under (a) highly reflecting conditions (ui = 1.33 = 1.09 = 13.43 = 0.97) and 

In the study of adsorbates, we define R/R as the normalized reflectance change for a bare surface due to the formation of an adlayer  

With the help of Fresnel s equations, the exact expressions for AR/R can be obtained by calculating the reflection coefficients for the three-phase system [Ri23 = R d)] and for the two-phase system [Ri = R 0)]. Such calculations. 

FIGURE 9. Three-phase model with sharp boundaries for the electrode/electrolyte interface. After Ref. 11. 

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