LINEAR-POLARIZATION DISCRIMINATION FOR IN-SITU INFRARED-SPECTROSCOPY AT ELECTRODE SURFACES

Linear polarization absorption ratios are determined from data for car bon monoxide and bisulfate anion adsorbed on Pt single crystal electro des and are compared to the extinction coefficient for the wire grid p olarizer utilized. The two adsorbates are at sub-monolayer coverages a nd have dipole moments, for the IR modes observed, which are normal to the electrode surface. Thus their intensities provide a direct measur e of the available parallel polarized light intensity regardless of th e actual Linear polarization state selected. From the relative absorpt ion ratios it is apparent that the linear polarization discrimination is much less than the predicted values from the polarizer extinction c oefficients. The decrease in extinction efficiency for the in situ mea surement as compared to the polarizer response is explained in terms o f the polarization rotation at the window/solution/electrode interface and the relative linear polarization throughput for the spectrometer.