Platinum Polarized light

Fig. 4. Reflectivity of parallel- and perpendicular-polarized light at 1600 cm for the system Ge/Pt/ vacuum determined for platinum films of various thicknesses. In the calculations, the optical constants of bulk platinum were used nce = 4.0, npt = 5.71 + Z23.35. The angle of incidence was 45°. Calculations were performed according to the matrix formalism described in the text.

Several aspects of this system are not clear for example, what causes a bipolar band in the spectrum with s-polarized light and why has Pons [137] not observed the 2137cm feature A comprehensive survey of the spectroscopic features observed for thiocyanate at electrochemical interfaces was given by Corrigan et al. [113] for gold and silver and by Ashley et al. for gold, silver and platinum [123]. 

The setup for external reflection absorption spectroscopy is shown in Fig. 1. A PPy-covered platinum disc electrode is pressed against a ZnSe window, yielding a distance of some m between the electrode and the window. The electrochemical current of the oxidation process has to pass the thin electrolyte layer. Since only parallel-polarized light interacts with substances near a reflecting metal surface, the nt light was polarized in this way. The IR beam permeates the window, the electrolyte and the polymer and is reflected at the Pt surface. Only this part of the radiation (a in Fig. 1) contains information on the polymer absorption. Reflections at the window and the polymer surface b, c and d in Mg. 1), which also reach the detector, can lead to disturbing spectral features and have to be eliminated or corrected. ... 

Recently, more detailed information has been obtained by Bewick and Pons to elucidate the behavior of TCNE in solutions of TBAF in acetonitrile. For very low concentrations of TCNE, and using polarized light, it was shown that the molecule was adsorbed flat on the platinum surface. 

The ellipsometer used in this study is described elsewhere(3). It consists of a Xenon light source, a monochromator, a polarizer, a sample holder, a rotating analyzer and a photomultiplier detector (Figure 1). An electrochemical cell with two windows is mounted at the center. The windows, being 120° apart, provide a 60° angle of incidence for the ellipsometer. A copper substrate and a platinum electrode function as anode and cathode respectively. Both are connected to a DC power supply. The system is automated with a personal computer to collect all experimental data during the deposition. Data analysis is carried out by a Fortran program run on a personal computer. 

---