Victoria L. Shannon

Second harmonic generation studies of interfacial structure and dynamics

Abstract This review surveys the current state of the field of optical second harmonic generation as it pertains to the study of interfacial phenomena. The experimental and theoretical studies discussed examine fundamental issues regarding the source of the nonlinear polarizability at the interface. Also included are both equilibrium and time-resolved measurements of the structural and thermodynamic properties therein. Experimental investigations of a variety of solid materials in air, vacuum, solution, and in contact with other solids are considered. A discussion of recent studies of the liquid/liquid interface concludes this review.

The observation of rotational anisotropy in the second harmonic intensity from a Ag(111) electrode

Rotational anisotropy in the second harmonic intensity is observed for a Ag(111) electrode and is compared to theory. The three and sixfold symmetric patterns for the p and s polarized SH fields reflect the ordered (111) crystal surface and demonstrate the promise of SHG as an in situ probe of surface structure at the electrode/electrolyte interface.

Second harmonic generation for in situ analysis of electrode surface structure

The nonlinear optical technique of second harmonic generation has been used as an in situ probe of surface structure and symmetry at the electrode-electrolyte interface. Rotational anisotropy in the second harmonic (SH) signalprovides valuable information on the degree of structural order at the metal surface. For Ag(111), the observed patterns in the p-and s-polarized SH output agree with current theories and demonstrate that an ordered surface is present. These patterns change as the electrode is electrochemically roughened.

Optical second-harmonic generation as an in situ probe of electrode surface dynamics. Ag(111)

Abstract Time-dependent changes are observed in the p-polarized optical second-harmonic generation from Ag(111) electrode surfaces as they are biased between the limits of the ideally polarizable region in Na 2 SO 4 and KCl electrolytes. Two different time constants are observed for changes in the SH response when the electrode is biased in the cathodic direction. The fast time behavior is attributed to potential-dependent alterations in the optical properties of the surface and surface adatom migration is suggested as a possible mechanism for the slow time behavior. The results demonstrate the versatility of this technique as a probe of electrode surface dynamics.

Monitoring surface structure and interfacial properties via second harmonic generation

Several studies are presented which demonstrate the application of SHG to the study of interfaces. Results are reported for experiments correlating the 511 signal from the electrochemical silver/aqueous electrolyte junction with the electrostatics of the interface as simultaneously monitored by differential capacitance. For related studies, in situ measurements of the surface morphology and structural symmetry of immersed Ag(111) surfaces are presented. The third set of experiments examines the surface SHG from several technologically important semiconducting chalcogenide materials under ambient conditions.