Electron energy loss spectroscopy description

This review aims to provide chemists working on porous materials with a basic understanding of XAS and related methods and to show them where the techniques might be of help in their research. After a short section on the basic physics of the interaction of X-rays with matter (Sect. 2), the basic physical processes and a theoretical description of XAFS are discussed (Sect. 3) in such a way that the method can be understood. Section 4 presents some experimental details and an example of a typical data analysis procedure. The next section is devoted an explanation of the type of information contained in X-ray absorption spectra by using examples from zeoHte chemistry (Sect. 5). Newer developments, especially with regard to time-resolved and in situ studies, as well as related techniques such as electron energy loss spectroscopy (EELS) and anomalous diffraction, are described in Sect. 6. 

After a brief description of the fundanietitals of High Resolution Electron Energy Loss Spectroscopy (HREELS), its potentialities in elucidating chemical reactions at a metal-polymer interface are illustrated by the well-known case of alunuRium evaporated onto polyimide (PMDA-OOA). Then the diHkuldes (but also the new promises) in roudnely applying this new spectroscopy to any metal-polymer sysKm will be shown for the copper-polyphenylquinoxaline interface. 

Buffle J, Wilkinson KJ, Stoll S, Filella M, and Zhang J (1998) A generalized description of aquatic colloidal interactions the three-colloidal component approach. Environmental Science and Technology 32 2887-2899. Egerton RE (1996) Electron Energy-Loss Spectroscopy in the Electron Microscope, 2nd edn. New York Plenum Press. 

FIGURE 13 Graded oxide nanoparticle. Mo02 was oxidized with air at 723 K to give a core-shell structure of molybdenum dioxide and possibly molybdenum trioxide that was identified by its different electron energy loss spectrum. No structural description of the highly disordered and catalytically relevant outer oxide shell could be determined, either with XRD or with TEM, (or even with EXAFS spectroscopy) as the signals are dominated by the core structure. 

In summary, the plasmon can be taken as a quantum-mechanical analog of the classical resonance of sufficiently high electron density. Such a description of excitations can be appropriate for energy-loss spectroscopy and related methods. For dipole interaction with the electromagnetic field it seems that the existence conditions for plasmons cannot be fulfilled at all because the Brillouin theorem does not account for electron-electron... 

In order to appreciate these and other results of yield spectroscopy on NEA diamond surfaces, it is best to recall briefly Spicer s three-step model of photoelectron emission, which is likely to be nowhere better suited than in the case at hand [109]. This model divides the photoelectron emission process up into three conceptually separate processes, (i) The bulk absorption of light generates photoexcited electrons and holes, and (ii) electrons travel to the surface with the possibility to suffer inelastic losses on their way before they (iii) escape into vacuum where they are being detected. In normal photoelectron spectroscopy interest lies in the so-called primary current, that is, in those electrons that leave the sample without energy loss on their way to the surface. In this case, the photoexcitation, transport, and escape processes are not entirely independent. For crystalline samples with well-ordered surfaces, the wave vector component parallel to the surface, k, is, for example, conserved from the initial electron state to the free electron in vacuum. In this case, a better description of the photoelectron emission is by a one-step excitation from an initial band structure state to a final state constructed as an inverse LEED state (Chapter 3.2.2). The inelastic mean free path of photoexcited electrons, is energy dependent and lies in the nanometer range (Chapter 3.2.3). 

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