Surface vibrations spectroscopy

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... 

Zhu X D, Suhr H and Shen Y R 1987 Surface vibrational spectroscopy by infrared-visible sum frequency generation Phys. Rev. B 35 3047-59... 

J. Phys. Chem. B, 106, 5143-5154. Somorjai, G. A. and Rupprechter, G. (1999) Molecular studies of catalytic reactions on crystal surfaces at high pressures and high temperatures by infrared-visible sum frequency generation (SFG) surface vibrational spectroscopy. J. Phys. Chem., 103, 1623-1638. 

Li X, Gewirth AA. 2003. Peroxide electroreduction on Bi-modified An surfaces Vibrational spectroscopy and density functional calculations. J Am Chem Soc 125 7086-7099. 

Bonn M, Hess C, Miners JH, Heinz TP, Bakker HJ, Cho M. 2001. Novel surface vibrational spectroscopy Infrared-infrared-visible sum-frequency generation. Phys Rev Lett 86 1566-1569. 

Cho M, Hess C, Bonn M. 2002. Lateral interactions between adsorbed molecules Investigations of CO on Ru(OOl) using nonlinear surface vibrational spectroscopies. Phys Rev B 65 ... 

Pdf 1111-CN. The usual bonding geometry for an adsorbed diatomic molecule is the end-on configuration where the molecular axis is perpendicular to the surface, as in the case of Ni 100)-C0 described above. This observation is consistent with the behaviour of CO, NO or N2 as ligands in co-ordination chemistry. By the same token we would perhaps expect a surface CN species also to be "terminally" bonded via the C atom as is normally found in cyano complexes. Surface vibrational spectroscopy has, however, indicated that surface CN formed by the decomposition of C2N2 on Pd and Cu surfaces is adsorbed in a lying-down configuration [16]. This result has since been confirmed by NEXAFS [17] and has led to a new consideration of the photoemission data from adsorbed CN [ 18]. 

The above discussion is meant to point out specific possible application of surface vibrational spectroscopy to new areas of catalysis. Certainly there are many others and brevity prevents further discussion of such a large subject. Reflection IR, IETS and perhaps Raman, which is rapidly developing in useful directions, would appear to have a good future as high resolution techniques for studies of the chemisorption of organic molecules on a variety of substrates. 

In 1987 he was promoted to distinguished member of the technical staff and technical manager. His efforts broadened to include projects on polymer-surface interactions adhesion promotion corrosion protection chemical vapor deposition and thin film growth optical fiber coating synthesis, structure, and reactivity of model organic surfaces and time-resolved surface vibrational spectroscopy. 

Although X-ray crystallography, NMR, and circular dichroism are extremely valuable techniques for determining the structure of crystalline proteins or proteins in solution, they cannot be used to study proteins adsorbed on surfaces. Vibrational spectroscopy (infrared and Raman) appears to be the best approach available for bridging the gap between adsorbed proteins and proteins in solution. 

Vibrational sum-frequency spectroscopy (VSFS) is a second-order non-linear optical technique that can directly measure the vibrational spectrum of molecules at an interface. Under the dipole approximation, this second-order non-linear optical technique is uniquely suited to the study of surfaces because it is forbidden in media possessing inversion symmetry. At the interface between two centrosymmetric media there is no inversion centre and sum-frequency generation is allowed. Thus the asynunetric nature of the interface allows a selectivity for interfacial properties at a molecular level that is not inherent in other, linear, surface vibrational spectroscopies such as infrared or Raman spectroscopy. VSFS is related to the more common but optically simpler second harmonic generation process in which both beams are of the same fixed frequency and is also surface-specific. 

Adsorbed carbon monoxide is a matter of special interest in ultrahigh vacuum as well as in electrochemical systems. CO has been used as probe molecule in surface vibrational spectroscopy. For important reviews of CO adsorbed from the gas phase, see [21, 42, 45, 46]. The rather large dynamic dipole moment (9///0Q) of adsorbed CO is particulary suited for infrared spectroscopy at electrochemical interfaces, where submonolayer amounts of species must be observed in the presence of IR-active solution compontents. 

The results of the studies presented above clearly demonstrate that SFG surface vibrational spectroscopy, when combined with appropriate calibration measurements, is a promising experimental method for bridging the pressure gap as well as the materials gap which separate the UHV single-crystal model studies from technical catalytic investigations. Further experimental work is under way in which the method developed in the present work will be applied to investigate the influence of surface structure, mixture composition and pressure on the ignition behavior of the CO/02/Pt-system and other reactants/surface-systems under technically relevant conditions. 

Somorjai GA, McCrea KR (2000) Sum frequency generation Surface vibrational spectroscopy studies of catalytic reactions on metal single-crystal surfaces. Adv Catal 45 385... 

Bonn M, Hess C, Funk S, Miners JH, Persson BNJ, Wolf M, Ertl G (2000) Femtosecond surface vibrational spectroscopy of CO adsorbed on Ru(OOl) during desorption. Phys Rev Lett 84 4653... 

Rupprechter G (2001) Surface vibrational spectroscopy from ultrahigh vacuum to atmospheric pressure Adsorption and reactions on single crystals and nanoparticle model catalysts monitored by sum frequency generation spectroscopy. Phys Chem Chem Phys 3 4621... 

High resolution electron energy loss spectroscopy (HREELS) is a form of surface vibrational spectroscopy in which the difference in energies between an impinging and a scattered electron beam provides information about the vibrational modes of a surface species. The apparatus is similar to that used in AES, in that an electron beam serves as the excitation source. However, because one must make precise measurements with resolutions in the meV range, the excitation electron beam is made monochromic to within... 

Park, S., S.A. Wasileski, and M.J. Weaver, Some interpretations of surface vibrational spectroscopy pertinent to fuel-cell electrocatalysis. Electrochimica Acta, 2002. 47(22-23) pp. 3611-3620... 

A major difference between SFG and other surface vibrational spectroscopy techniques is the presence of a non-resonant background, because, in part, of the metal substrate. This background is usually treated as independent of the frequency and characterized as a constant ( nr). although this treatment is not always possible. In electrochemical systems, /nr is not usually independent of the applied potential. This is because of potential-dependent changes in the electronic state... 

RAIRS results in a spectrum that is similar to that of a transmission measurement For grazing incidence geometry, only molecular vibrations giving rise to a dynamic dipole perpendicular to the surface are infrared active this is termed the surface selection rule for surface vibrational spectroscopy. 

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