Spectroscopy near-edge

In the case of surface sites incorporating atoms, the valence states and their eventual variation in the course of the reaction can be studied by spectroscopic methods such as electron paramagnetic resonance (EP.R), XPS, ultra-violet photoelectron (UPS), IR, and near-edge X-ray (XANES) spectroscopies (Near-edge X-ray spectroscopy is abbreviated in some parts of the world, particularly in USA, as NEXASS). 

Coey JMD (1980) Clay minerals and their transformation studied with nuclear techniques the contribution of Mossbauer spectroscpoy. Atomic Energy Rev 18 73-124 Colliex C, Manoubi T, Ortiz C (1991) Electron energy-loss spectroscopy near-edge fine stracture in the iron-oxygen system. Phys Rev B 44 11402-11411... 

Keywords Conjugated molecules. Semi-empirical models and model calculations. Synchrotron radiation photoelectron spectroscopy. Near edge X-ray absorption fine structure... 

Among techniques used to characterize such LB CP films have been low angle x-ray diffraction, comparative transmission-mode and reflection-mode IR spectroscopy, near-edge X-ray absorption fine structure (NEXAFS), and of course, conductivities, determined by transfer of LB films onto special 4-electrode substrates. As expected especially for the LB CP films which include alternating non-conductive surface-active molecular layers, conductivities of such films are highly anisotropic. For example, the conductivity of Shimidzu et al. s poly(3-octadecyl 4-Me-pyrrole-3-carboxylate)/octadecane alternating layer film, described above, is 10 S/cm in-plane and 10 S/cm across the film, yielding a conductivity anisotropy of 10 . 

Zaera F, Fischer D A, Shen S and Gland J L 1998 Fluorescence yield near-edge X-ray absorption spectroscopy under atmospheric conditions CO and FI2 coadsorption on Ni(IOO) at pressures between 10 and 0.1 Torr Surf. Sc/. 194 205-16... 

Fischer D, Marti A and Hahner G 1997 Orientation and order in microcontact-printed, seif-assembied monoiayers of aikanethiois on goid investigated with near edge x-ray absorption fine structure spectroscopy J. Vac. Sc/. Technol. A 15 (4) 2173-80... 

Near edge x-ray absorption fine stmcture spectroscopy (nexafs) and x-ray photoelectron spectroscopy (xps) have been used to study SAMs of OTS, octadecyltrimethoxysilane (OTMS), CH2(CH2) ySi(OCH2)3, and (17-aminoheptadecyl)-trimethoxysilane (AHTMS), H2N(CH2) ySi(OCH3)3 (149). A number of important observations have been reported. First, the chains in OTS SAMs are practicaUy perpendicular to the substrate surface (tilt angle... 

EXAFS is part of the field of X-ray absorption spectroscopy (XAS), in which a number of acronyms abound. An X-ray absorption spectrum contains EXAFS data as well as the X-ray absorption near-edge structure, XANES (alternatively called the near-edge X-ray absorption fine structure, NEXAFS). The combination of XANES (NEXAFS) and EXAFS is commonly referred to as X-ray absorption fine structure, or XAFS. In applications of EXAFS to surface science, the acronym SEXAFS, for surface-EXAFS, is used. The principles and analysis of EXAFS and SEXAFS are the same. See the article following this one for a discussion of SEXAFS and NEXAFS. 

Amorphous carbon films may be broadly classified as (i) amorphous carbon films, a-C films, deposited from carbon-containing gases with low or zero hydrogen content [72] and (ii) hydrogenated carbon films, a-C H films, formed from hydrocarbon-containing gases [73,74]. Both types of film contain different amounts of sp and sp bonded carbon. The amount of sp bonded carbon can be estimated from X-ray absorption near edge spectroscopy,... 

X-ray absorption near edge structure (XANES) spectroscopy is a non-destructive and sensitive probe of the coordination number and geometry as well as of the effective charge of a chosen atom within a molecule and therefore also of the formal oxidation number. Recently, there have been a number of XANES studies at the sulfur K-edge demonstrating the sensitivity of... 

X-ray absorption near-edge spectroscopy (XANES) suggests that, in most of the enzymes, the reduction to Ni-SI also implies a change in the coordination number of the Ni ion from 5 to 6 (74). 

X-ray absorption spectroscopy combining x-ray absorption near edge fine structure (XANES) and extended x-ray absorption fine structure (EXAFS) was used to extensively characterize Pt on Cabosll catalysts. XANES Is the result of electron transitions to bound states of the absorbing atom and thereby maps the symmetry - selected empty manifold of electron states. It Is sensitive to the electronic configuration of the absorbing atom. When the photoelectron has sufficient kinetic energy to be ejected from the atom It can be backscattered by neighboring atoms. The quantum Interference of the Initial... 

The shape of the edge itself examined by XANES (X-ray near-edge spectroscopy) can be employed to reveal information on d-band vacancy concentration vs. treatment. The oscillations at energies above the edge (EXAFS) ctui provide information on near-neighbor atom spacing tuid some limited information on the chemical environment. As we will show, the best way to use such tools is to use several at once, rather them only one. 

Evidence for the first reason was demonstrated in X-ray photoelectron spectroscopy (XPS) or X-Ray Absorption Near Edge Structure (XANES) studies, as well as by many voltammetric studies. ... 

XANES X-ray absorption near edge structure spectroscopy... 

Elder, R.C., Tepperman, K.G., Eidsness, M.K., Heeg, M.J., Shaw, C.F. Ill and Schaeffer, N. A. (1983) Gold-based antiarthritic drugs and metabolites. Extended x-ray adsorption fine structure (EXAFS) spectroscopy and x-ray absorption near edge spectroscopy (XANES). ACS Symposium Series, 209, 385-400. 

The deposition conditions should be optimized to obtain approximately equal amounts of matrix and spreader-bar molecules on the surface [18,21]. Analysis of monolayers by near-edge X-ray absorption fine-structure spectroscopy. 

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