| Abstract
| - A mathematical framework is presented for the quantitative analysis of in situ potential modulation spectroelectrochemical techniques based on phase-sensitive detection for the study of solution-phase redox systems understrict diffusion control. In the case of arrangements inwhich the probing beam is parallel to the electrodesurface, the phase of the optical signal with respect to theapplied potential, assuming negligible double-layer charging currents, was found to be proportional to y(ω/2D)1/2,where y is the distance normal to the electrode, ω is thefrequency of the perturbating signal, and D is the diffusioncoefficient of the species responsible for absorption orrefraction. Good agreement was found between theoreticalpredictions and the few available experimental results forboth absorption and probe beam deflection-type experiments. In particular, in the case of solutions containingthe chromophore trianisylamine and nonabsorbing p-benzoquinone, the phase angle difference between absorption and diffraction calculated from theory and measured experimentally yielded a common value of ∼30°.
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