DETERMINING ELECTRODE POSITION AND SOURCE COHERENCE IN SPECTROELECTROCHEMICAL ANALYSES WITH PARALLEL GEOMETRIES

Whenever a monochromatic collimated light beam illuminates a planar el ectrode surface parallel to that surface, a diffraction pattern charac teristic of the beam's coherence is obtained. The electrode edge posit ion is generally determined utilizing a procedure which assumes either a totally coherent or an incoherent source. In this work, the image o f the diffraction pattern was magnified and focused on a diode array, and the resulting intensity profile was compared with that obtained fr om a slightly defocused image. Perturbation theory was applied to pred ict the position of the electrode's edge. Once the edge position was k nown, the source's coherence was determined from the normalized intens ity at the electrode's edge. This technique can be utilized in situ wi th ''parallel'' spectroelectrochemical experiments. It does not depend on a priori knowledge of the light source's coherence nor does it req uire an opaque-translucent interface. A simple model and experimental data employing this method are presented. Measurements of the experime ntal electrode positions were reproducible within the theoretical magn ifier/array limit, 1 mu m