This project is in the general area of analytical and surface chemistry and in the subfields of surface vibrational spectroscopy and electrochemistry. Unenhanced surface Raman spectroscopy (SURS) will be developed as an analytical tool for studies of adsorption and reaction in electrochemical systems and to study short-range or chemical enhancement in surface- enhanced Raman spectroscopy (SERS). Charge-coupled device detectors will be employed to increase optical detection sensitivity by more than an order of magnitude, thereby making a wide range of surface chemical systems accessible for study. Orientational phase transitions and electrochemical reaction pathways will be studied on smooth electrode surfaces using SURS as an in situ probe of the molecular nature of the adsorbed species. Comparisons will be made to systems previously studied using SERS. Electron spectroscopic studies using high resolution electron energy loss spectroscopy combined with Raman excitation profiles and cross-section measurements will be used to study chemical effects in SERS studies of well-characterized model systems. Unenhanced surface Raman spectroscopy is a powerful probe of the structures and reactions of molecules adsorbed on solid surfaces in ultrahigh vacuum, in high pressure gas ambient phases and in the electrochemical environment. It offers high molecular specificity, high spectral and spatial resolution and relatively high sensitivity. In contrast to surface-enhanced Raman spectroscopy, this technique does not depend on the electronic properties and surface structure of the substrate, which may be a metal, semiconductor or dielectric.
