Spectroscopy interface

Given the interest and importance of chiral molecules, there has been considerable activity in investigating die corresponding chiral surfaces [, and 70]. From the point of view of perfomiing surface and interface spectroscopy with nonlinear optics, we must first examhie the nonlinear response of tlie bulk liquid. Clearly, a chiral liquid lacks inversion synnnetry. As such, it may be expected to have a strong (dipole-allowed) second-order nonlinear response. This is indeed true in the general case of SFG [71]. For SHG, however, the pemiutation synnnetry for the last two indices of the nonlinear susceptibility tensor combined with the... 

The SHG/SFG technique is not restricted to interface spectroscopy of the delocalized electronic states of solids. It is also a powerful tool for spectroscopy of electronic transitions in molecules. Figure Bl.5.13 presents such an example for a monolayer of the R-enantiomer of the molecule 2,2 -dihydroxyl-l,l -binaphthyl, (R)-BN, at the air/water interface [ ]. The spectra reveal two-photon resonance features near wavelengths of 332 and 340 mu that are assigned to the two lowest exciton-split transitions in the naphtli-2-ol... 

ISAS — Institute for Analytical Sciences, Department for Interface Spectroscopy, Albert-Einstein-Str. 9, 12489 Berlin, Germany... 

Tadjeddine A and Peremans A (1998) In Clark RJH and Hester RE (eds.) Non-linear Optical Spectroscopy of the Electrochemical Interface. Spectroscopy for Surface Science. London Wiley. 

The varying actual orientation of molecules adsorbed at an aqueous solution-CCU interface with decreasing A has been followed by resonance Raman spectroscopy using polarized light [130]. The effect of pressure has been studied for fatty alcohols at the water-hexane [131] and water-paraffin oil [132] interfaces. 

The detailed examination of the behavior of light passing through or reflected by an interface can, in principle, allow the determination of the monolayer thickness, its index of refiraction and absorption coefficient as a function of wavelength. The subjects of ellipsometry, spectroscopy, and x-ray reflection deal with this goal we sketch these techniques here. 

The interface between a solid and its vapor (or an inert gas) is discussed in this chapter from an essentially phenomenological point of view. We are interested in surface energies and free energies and in how they may be measured or estimated theoretically. The study of solid surfaces at the molecular level, through the methods of spectroscopy and diffraction, is taken up in Chapter VIII. 

Flimpsel F J, McFeely F R, Morar J F, Taleb-lbrahimi A and Yarmoff J A 1990 Core level spectroscopy at silicon surfaces and interfaces Proc. Enrico Fermi School on Photoemission and Adsorption Spectroscopy and Interfaces with Synchrotron Radiation vo course CVIII, eds M Campagna and R Rose (Amsterdam Elsevier) p 203... 

Seah M P and Dench W A 1979 Quantitative electron spectroscopy of surfaces a standard data base for electron inelastic mean free paths in solids Surf, interface Anai. 1 2... 

Iwasita T and Mart F C 1997 In situ infrared spectroscopy at electrochemical interfaces Prog. Surf. Sc/. 55 271... 

Raduge C, Pfiumio V and Shen Y R 1997 Surface vibrational spectroscopy of sulfuric acid-water mixtures at the liquid-vapor interface Chem. Phys. Lett. 274 140... 

Shen Y R 1998 Sum frequency generation for vibrational spectroscopy applications to water interfaces and films of water and ice Solid State Commun. 108 399... 

Because of the generality of the symmetry principle that underlies the nonlinear optical spectroscopy of surfaces and interfaces, the approach has found application to a remarkably wide range of material systems. These include not only the conventional case of solid surfaces in ultrahigh vacuum, but also gas/solid, liquid/solid, gas/liquid and liquid/liquid interfaces. The infonnation attainable from the measurements ranges from adsorbate coverage and orientation to interface vibrational and electronic spectroscopy to surface dynamics on the femtosecond time scale. 

We now present one of the many examples of interfacial vibrational spectroscopy using SFG. Figure Bl.5.15 shows the surface vibrational spectrum of the water/air interface at a temperature of 40 °C [83]. Notice that... 

Dumas P, Weldon M K, Chabal Y J and Williams G P 1999 Molecules at surfaces and interfaces studied using vibrational spectroscopies and related techniques Surf. Rev. Lett. 6 225-55... 

Bain C D 1995 Sum-frequency vibrational spectroscopy of the solid-liquid interface J. Chem. See. Faraday Trans. 91 1281-96... 

Eisenthal K B 1996 Liquid interfaces probed by second-harmonic and sum-frequency spectroscopy Chem. Rev. 96 1343-60... 

Richmond G L 1997 Vibrational spectroscopy of molecules at liquid/liquid interfaces Ana/. Chem. 69 A536-43... 

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... 

Heinz T F, Himpsel F J, Palange E and Burstein E 1989 Electronic transitions at the CaF2/Si(111) interface probed by resonant three-wave-mixing spectroscopy Phys. Rev. Lett. 63 644-7... 

Hicks J M, Petralli-Mallow T and Byers J D 1994 Consequences of chirality in second-order nonlinear spectroscopy at interfaces Faraday Disc. 99 341 -57... 

Du Q, Superfine R, Freysz E and Shen Y R 1993 Vibrational spectroscopy of water at the vapor-water interface Phys. Rev. Lett. 70 2313-16... 

Every property of an interface that can be optically probed can, in prmciple, be measured with the SEA. This may include infonnation obtainable from absorption spectroscopy [M], fluorescence, dicln-oism, birefringence, or nonlinear optics [43], some of which have already been realized. 

The power of optical spectroscopies is that they are often much better developed than their electron-, ion- and atom-based counterparts, and therefore provide results that are easier to interpret. Furtlienuore, photon-based teclmiques are uniquely poised to help in the characterization of liquid-liquid, liquid-solid and even solid-solid interfaces generally inaccessible by other means. There has certainly been a renewed interest in the use of optical spectroscopies for the study of more realistic systems such as catalysts, adsorbates, emulsions, surfactants, self-assembled layers, etc. 

Figure Bl.22.4. Differential IR absorption spectra from a metal-oxide silicon field-effect transistor (MOSFET) as a fiinction of gate voltage (or inversion layer density, n, which is the parameter reported in the figure). Clear peaks are seen in these spectra for the 0-1, 0-2 and 0-3 inter-electric-field subband transitions that develop for charge carriers when confined to a narrow (<100 A) region near the oxide-semiconductor interface. The inset shows a schematic representation of the attenuated total reflection (ATR) arrangement used in these experiments. These data provide an example of the use of ATR IR spectroscopy for the probing of electronic states in semiconductor surfaces [44]-...

McGlip J F 1990 Epioptics linear and non-linear optical spectroscopy of surfaces and interfaces J. Phys. Condens Matter 2 7985-8006... 

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