| Time-resolved vibrational sum and difference frequency studies are reported for the cyanide anion on Pt(111), Au, Ag, Cu, Cu(111), and Pt(disorded) surfaces in an electrochemical environment. The lifetime trends that the CN stetching vibration exhibits with electrochemical potential, metal composition, and solvent are examined. The results are interpreted in the context of both an image-dipole and a charge-transfer relaxation mechanism.; Absolute intensity measurements of the optical second harmonic response (0.7–2.5 eV) are reported for Ag(111), Ag, decanethiol on Ag, 4-aminothiophenol on Ag, Cu(111), and Au surfaces in an electrochemical environment. The magnitude and frequency dependence of the second harmonic response are compared to predictions from a free-electron theory for the nonlinear optical response of metals. The effects that electrochemical potential and chemisorption have on the second harmonic spectra are also examined. The frequency range and metals for which the free-electron theory is adequate are identified. |
