Second harmonic generation surface studies

Y., and Somorjai, G. (1986). Studies of alkali adsorption on Rh(lll) using optical second-harmonic generation. Surface Science, 172 466 - 476. 

Petraiii-Maiiow T, Wong T M, Byers J D, Yee H i and Hicks J M 1993 Circuiar dichroism spectroscopy at interfaces—a surface second harmonic-generation study J. Phys. Chem. 97 1383-8... 

Sitzmann E V and Eisenthal K B 1988 Picosecond dynamics of a chemical-reaction at the air-water interface studied by surface second-harmonic generation J. Phys. Chem. 92 4579-80... 

Zhu X D, Rasing T H and Shen Y R 1988 Surface diffusion of CO on Ni(111) studied by diffraction of optical second-harmonic generation off a monolayer grating Phys. Rev. Lett. 61 2883-5... 

Shi Z, Lipkowski J, Mirwald S and Pettinger B 1996 Electrochemical and second harmonic generation study of bromide adsorption at the Au(111) surface J. Chem. See. Faraday Trans. 92 3737-46... 

According to the data obtained with SXRS in salt solutions,519 520 at a < 0 the surface of Au(lll) forms a ( 3 x 22) structure as in a vacuum. At a > 0 the reconstruction disappears and the (1 x 1) structure is observed. On the reconstructed Au(l 11) surface there are 4.4% more atoms than on the (1 x 1) structure and on the reconstructed Au( 100) there are 24% more atoms than on the (1 x 1) structure.506,519 This phase transition shifts in the negative direction with the adsorbability of the anion. The adsorption-induced surface reconstruction of Au(l 11) electrodes has been studied in situ by second harmonic generation by Pettinger et al.521... 

Com, R. M., In situ second harmonic generation studies of molecular orientation at electrode surfaces, in Adsorption of Molecules at Metal Electrodes, J. Lipkowski and P. N. Ross, Eds., VCH, New York, 1992, p. 391. 

In recent years,3 4 however, there has been renewed interest in the study of the electrode/solution interface due in part to the development of new spectroscopic techniques such as surface-enhanced Raman spectroscopy,5-7 electrochemically modulated infrared reflectance spectroscopy and related techniques,8,9 second-harmonic generation,10-12 and others which give information about the identity and orientation of molecular species in the interfacial... 

In the following sections we will first in Section 2 briefly discuss the necessary background to understand optical activity effects in linear and nonlinear optics and to illustrate the similarities and differences between both types. In Section 3 we present a more thorough analysis of nonlinear optical effects in second-harmonic generation, both from a theoretical and an experimental point of view. Section 4 deals with experimental examples that illustrate the usefulness of nonlinear optical activity in the study of chiral thin films and surfaces. Finally, in Section 5 we give an overview of the role of chirality in the field of second-order nonlinear optics and show that chiral molecules can be useful for applications in this field. 

Second Harmonic Generation Studies of Chemisorption at Electrode Surfaces... 

Optical second harmonic generation from electrode surfaces is employed in situ to study the... 

In addition to the indirect experimental evidence coming from work function measurements, information about water orientation at metal surfaces is beginning to emerge from recent applications of a number of in situ vibrational spectroscopic techniques. Infrared reflection-absorption spectroscopy, surface-enhanced Raman scattering, and second harmonic generation have been used to investigate the structure of water at different metal surfaces, but the pictures emerging from all these studies are not always consistent, partially because of surface modification and chemical adsorption, which complicate the analysis. 

Bilger and Pettinger ]17] have applied second-harmonic generation (SHG) method to study the anisotropy of Au(l 10) electrode in a wide potential range from —0.60 to 0.60 V, corresponding to the transition from the microfaceted to the unreconstructed surface. 

The SHG surface spectroscopy is another method useful in the studies on halide adsorption. ApplicabiKty of the SHG spectroscopy method to Au surface properties has been discovered by Pettinger, Kolb, and coworkers [74, 75]. It has also been shown that reconstruction of Au(lll) and Au(lOO) electrodes remarkably affects SHG anisotropy [74]. For this reason, an interference second-harmonic generation anisotropy (ISHGA)... 

FLC phases in the surface stabilized geometry possess a single C2 axis of symmetry, and therefore polar order and non-zero x<2) in the simple electronic dipolar model. Thus, it is not surprising that experiments aimed at measuring this property were first reported shortly after the Clark-Lagerwall invention. Early studies (14-15) described second harmonic generation in (S)-2-Methylbutyl 4-(4-decyloxybenzylideneamino)cin-namate, the first ferroelectric liquid crystal, also known as DOBAMBC (1). 

In the first study of its kind, second harmonic generation has been used to study potential induced reconstruction on Au(lll) and Au(100) by Kolb and coworkers [156]. These surfaces have been known to reconstruct in UHY when they are clean [153, 157], Surface reconstruction occurs when the surface atoms of a solid rearrange themselves in a structure different from that expected from simple termination of the bulk lattice. Various studies by cyclic voltammetry, electroreflectance spectroscopy and ex situ electron diffraction have suggested that flame-treated crystals form stable reconstructions in solution. Unfortunately, due to the lack of in situ probes, very little direct evidence for this reconstruction has been available. 

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