Scattered photoelectrons

Previous work by our and other groups has shown that the Pt L3 XANES is sensitive to the adsorption of H. This sensitivity was interpreted by our group as being caused by the creation of a chemical bond between Pt and H30. The Pt-H anti-bonding state (AS) above the Fermi level was thought to produce a shaperesonance arising from the interference between the resonantly and nonresonantly scattered photoelectron waves. 

Figure 8.35 Interference between scattered photoelectrons in (a) a gaseous diatomic molecule and (b) a crystalline material...

In section 2.3 we have decomposed various surface-sensitive techniques into a small set of more elementary processes. In this section we shall present appropriate formalisms that describe these individual processes. Namely, we shall discuss the theoretical treatment of the propagation of electrons in the surface region, as well as the treatment of elastic and inelastic electron-atom scattering, photoelectron emission and of Auger electron emission. These parts... 

The growth mode of Fe on Ni(OOl) was studied using forward-scattering photoelectron diffraction [35]. Figure 13 shows the I AD along the [110] azimuth for... 

The activated catalyst sample was examined by ESC A spectrometer (Perkin Elmer PHI 5400, USA). During the analysis an energy pass of 35 eV was used, with pressure lower than 2.7-10" kPa. Binding energy calibration was based on carbon impurity peak at 284.6 eV. Shirley background removal method was applied to remove the background of inelastically scattered photoelectrons. 

For a perfectly random distribution of very small crystals (powder) there would be no angular variation effect on the experimental XAS spectra however, for a fully oriented crystal structure such as that of a mica blade lying flat on the sample-holder, the amplitude of the scattered photoelectron wave depends on the angle a between the... 

Figure 2 Representation of the outgoing ( ij) and back-scattered photoelectron waves.

Egelhoff W F Jr 1990 X-ray photoelectron and Auger electron forward scattering a new tool for surface crystallography CRC Crit. Rev. Soiid State Mater. Sc/. 16 213... 

Figure A3.7.6. Photoelectron spectrum of. Here the F is complexed to para-R - Solid curve experimental results. Dashed curve simulated spectrum from scattering calculation on ab initio surface.

Vibrational spectroscopy provides detailed infonnation on both structure and dynamics of molecular species. Infrared (IR) and Raman spectroscopy are the most connnonly used methods, and will be covered in detail in this chapter. There exist other methods to obtain vibrational spectra, but those are somewhat more specialized and used less often. They are discussed in other chapters, and include inelastic neutron scattering (INS), helium atom scattering, electron energy loss spectroscopy (EELS), photoelectron spectroscopy, among others. 

The EXAFS technique is used primarily for investigations of disordered materials and amorphous solids. Figure 8.35(b) shows how interference occurs between the wave associated with a photoelectron generated on atom A and the waves scattered by nearest-neighbour atoms B in a crystalline material. 

Energy Spectrometry (EDS) uses the photoelectric absorption of the X ray in a semiconductor crystal (silicon or germanium), with proportional conversion of the X-ray energy into charge through inelastic scattering of the photoelectron. The quantity of charge is measured by a sophisticated electronic circuit linked with a computer-based multichannel analyzer to collect the data. The EDS instrument is... 

Figure 1 Simplistic schematic illustration of the scattering mechanism upon which X-ray photoelectron diffraction (XPD) is based. An intensity increase is expected in the forward scattering direction, where the scattered and primary waves constructively interfere.

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