EELS, energy-loss spectrum

Structural Information from EELS. Besides yielding chemical composition, EELS is also capable of providing structural information on an atomic scale. It has been known (54) for some time that the fine-structure in the energy-loss spectrum close to an ionization edge reflects the energy dependence of the density of electronic states above the Fermi level. 

For comparison with experimental data [100-102], it is common to evaluate the oscillator strengths, photo absorption cross section and EELS (Electron Energy Loss Spectrum) defined here in terms of the imaginary part of the polarizability 7 ... 

By application of valence shell electron energy loss spectroscopy, inner shell electron energy loss spectroscopy, magnetic circular dichroism spectroscopy, as well as photoelectron and electron transmission spectroscopy it can be deduced that the ji-electron system of borazine resembles that of benzene [8]. Table 4/13 presents the Rydberg term value matrix and Table 4/14 the energies and assignments from the electron energy loss spectrum (EELS) [8]. 

A very powerful method to study the electronic structure of solids is electron energy-loss spectroscopy (EELS). Because electrons transfer not only energy to the solid (as do photons) but also momentum, in addition to the energetic position of the electronic states, the dispersion of the bands can also be studied. Figure 1.58 shows the energy-loss spectrum of polypyrrole doped with the sulphonic acid H—(CH2)4—SO3 [126]. The various curves were recorded at different values of momentum transfer q. The dashed lines connect corresponding peaks. Vertical lines are characteristic of transitions into narrow bands (without dispersion), whereas inclined lines indicate broad bands. The maxima in the spectrum with low momentum transfer (bottom curve) are related to the maxima in the electronic joint density of states, but for... 

Litzelmann et al. [223] have used electron energy loss spectroscopy [EELS] to obtain information on the nature of the insulator-metal transition as a function of protonation. Their results indicate the momentum dependence of energy loss spectrum of electrons, which does not support polyaniline as a granular metal. Similarly, the NMR and ESR study by Mizoguchi et al. [224] indicates the absence of three-dimensional metallic islands, which again does not support polyaniline as a granular metal. 

EELS electron energy loss spectrum device... 

HREELS High-resolution electron energy-loss spectroscopy [129, 130] Same as EELS Identification of adsorbed species through their vibrational energy spectrum... 

It should be noted that low-loss spectra are basically connected to optical properties of materials. This is because for small scattering angles the energy-differential cross-section dfj/dF, in other words the intensity of the EEL spectrum measured, is directly proportional to Im -l/ (E,q) [2.171]. Here e = ei + iez is the complex dielectric function, E the energy loss, and q the momentum vector. Owing to the comparison to optics (jqj = 0) the above quoted proportionality is fulfilled if the spectrum has been recorded with a reasonably small collection aperture. When Im -l/ is gathered its real part can be determined, by the Kramers-Kronig transformation, and subsequently such optical quantities as refraction index, absorption coefficient, and reflectivity. 

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