In peak energies

Because the two states are so close in peak energy, one finds it difficult to delineate the actual excitation transition. 

Despite the failure of the activation of TCE on clusters observed in TPD, EES experiments of deposited selected clusters of similar sizes were performed. The exclusion of additional molecules and the chemisorption behavior for selected clusters, reduces the origin of possible shifts in peak energy positions in EE spectra to the effect of physisorption induced relaxation shifts. Thus, it allows for uncomplicated comparison of the differences in physisorption on the surfaces and supported clusters (if omitting compensating effects of potential energy and electron relaxation, as discussed in Sect. 2.2.4). 

Figure Bl.25.12. Excitation mechanisms in electron energy loss spectroscopy for a simple adsorbate system Dipole scattering excites only the vibration perpendicular to the surface (v ) in which a dipole moment nonnal to the surface changes the electron wave is reflected by the surface into the specular direction. Impact scattering excites also the bending mode v- in which the atom moves parallel to the surface electrons are scattered over a wide range of angles. The EELS spectra show the higlily intense elastic peak and the relatively weak loss peaks. Off-specular loss peaks are in general one to two orders of magnitude weaker than specular loss peaks.

Figure 4 Experimental low-loss profiles for Mg (10.0)< Ti (17.2), Zr(16.6), and their hydrides MgH2 (14.2), TiH 97 (20.0), and ZrHj g (18.1). The values in parentheses represent the experimental plasmon-loss peak energies in eV.

As mentioned above, the interpretation of CL cannot be unified under a simple law, and one of the fundamental difficulties involved in luminescence analysis is the lack of information on the competing nonradiative processes present in the material. In addition, the influence of defects, the surface, and various external perturbations (such as temperature, electric field, and stress) have to be taken into account in quantitative CL analysis. All these make the quantification of CL intensities difficult. Correlations between dopant concentrations and such band-shape parameters as the peak energy and the half-width of the CL emission currently are more reliable as means for the quantitative analysis of the carrier concentration. 

Fine structure extending several hundred eV in kinetic energy below a CEELS peak, analogous to EXAFS, have been observed in REELS. Bond lengths of adsorbed species can be determined from Surface Electron Energy-Loss Fine Structure (SEELFS) using a modified EXAFS formalism. 

Energy analyzers cannot be discussed without discussion of energy resolution, which is defined in two ways. Absolute resolution is defined as AE, the full width at half-maximum (FWHM) of a chosen peak. Relative resolution is defined as the ratio R of AE to the kinetic energy E of the peak energy position (usually its centroid), that is, R = AE/E. Thus absolute resolution is independent of peak position, but relative resolution can be specified only by reference to a particular kinetic energy. 

In XPS, closely spaced peaks at any point in the energy range must be resolved, which requires the same absolute resolution at all energies. 

Both of the current models for the central mode scattering contain the implicit assumption of cubic symmetry above Tm. Possibly because of the dramatic nature of the soft-mode behaviour and a ready understanding of the structural transformation in terms of it, there was a strong incentive to establish a link between it and the central mode scattering. A consistent difficulty with this approach is the failure to establish an intrinsic line-width for the central mode peak and the unspecified nature of the mechanism responsibly for a low-frequency resonance in the energy of the soft mode. ... 

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