Adsorber radial

Fig. 8.34 Surface sensing sensitivity of different radial order modes are simulated by using the perturbation method with the same azimuthal number m 700.The adsorbed polymer layer is assumed to have a refractive index of 1.46...

A part of Figure 3 in Ref. 207, reproduced on the right, reports radial EXAFS data around the S Is absorption edge for sulfur adsorbed on the (100) plane of a g nickel single-crystal surface. The top trace corresponds to the deposition of atomic S sulfur by dehydrogenation of H2S, while g, the bottom data were obtained by adsorb- M ing thiophene on the clean surface at 100 K. Based on these data, what can be learned about the adsorption geometry of thiophene Propose a local structure for the sulfur atoms in reference to the neighboring nickel surface. 

The structure of the adsorbed ion coordination shell is determined by the competition between the water-ion and the metal-ion interactions, and by the constraints imposed on the water by the metal surface. This structure can be characterized by water-ion radial distribution functions and water-ion orientational probability distribution functions. Much is known about this structure from X-ray and neutron scattering measurements performed in bulk solutions, and these are generally in agreement with computer simulations. The goal of molecular dynamics simulations of ions at the metal/water interface has been to examine to what degree the structure of the ion solvation shell is modified at the interface. 

PtSn-OM and PtSn-OM samples show a more complicated radial distribution function. At least two different scatterer atoms must be present to obtain such a result. Considering the way the catalysts are prepared, a Pt-C and a Pt-Pt shell were used to perform the fits. Before the reduction process, a solvent fraction remains adsorbed on the samples, so the appearance of C near the Pt atoms is natural. Results show that the coordination number for the Pt-Pt shell is smaller in both... 

Scanning Tunneling Microscopy. One way to get estimates for lateral interactions is STM. Using STM one can determine the statistical distribution of the adsorbates over the surface. This distribution can be converted into a radial distribution function, which in turn can be converted into effective lateral interactions. The accuracy of the value of a certain lateral interaction depends on the number of times it has been observed on the surface. Strongly repulsive interactions (larger than a few times k T) can therefore not be determined using this method. 

One has to be able to image the exact position of each adsorbate to obtain the radial distribution function. This requires a low adsorbate mobility, since a full scan typically takes one minute to do. This method is therefore mainly applied to atoms on low-temperature surfaces. The consequence of keeping the temperature low to suppress surface mobility is that the absolute value of the repulsive interactions that can be determined is also small, typically less than 10 kJ/mol at room temperature. 

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