Electron Energy Loss Spectroscopy spectra

High-resolution electron-energy-loss spectroscopy spectra of c(2x2) H/Fe(l 1 0) [191] are interpreted from selection rules, isotope effect, and wave number as H in the short bridge position [191]. 

High-resolution electron-energy-loss spectroscopy spectra of CO/Fe(110) indicate that CO is positioned on-top with the C-O stretching frequency at 1890-1950cm [428]. The vibration frequency for the C-O stretch for... 

On Fe(l 1 1) 3 different coordinations have been observed [437]. High-resolu-tion electron-energy-loss spectroscopy spectra of C + 0/Fe(l 11) show the Fe-C stretch at 420 cm and the Fe-O stretch at 540 cm [437]. 

High-resolution electron-energy-loss spectroscopy spectra of N2 /Fe(l 11) show a N-N stretch at 1490 cm [463, 470, 472] indicating a considerable weakening of the N-N bond compared to the stretch found at 435 cm [463, 472]. 

High-resolution electron-energy-loss spectroscopy spectra of NH3/Fe( 110) at 120-315 K were reported and interpreted [540, 546]. The geometry of the adsorbed molecule is C3V, i.e., the symmetry of the surface has a negligible effect on the adsorbed molecule. The high-resolution electron-energy-loss spectroscopy spectra are interpreted [540] as Fe-N stretch at 420 cm for NH3, 400 cmfor ND3 /Fe, symmetrical NH3 stretch at 1170cm for NH3, 905 cm for ND3, symmetrical NH3 stretch at 3310 cm for NH3, 2410 cm for ND3 +. ... 

The most direct information on the origin of the effects comes from quantum mechanical calculations and single crystal chemisorption studies. From single crystal studies it is concluded that the effect of K is to increase the stability of N2 [466]. High-resolution electron-energy-loss spectroscopy spectra of N2 Fe(l 11) and N2 /K/Fe(l 1 1) show that K does not promote the dissociation of N2 by weakening the N-N bond in N2 [475]. 

The geometry of N2 is assigned to side-on based on detailed interpretation of the X-ray photoelectron spectroscopy spectrum [460, 461] and of the high-resolution electron-energy-loss spectroscopy spectrum [470]. 

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

Analytical electron microscopy (AEM) can use several signals from the specimen to analyze volumes of catalyst material about a thousand times smaller than conventional techniques. X-ray emission spectroscopy (XES) is the most quantitative mode of chemical analyse in the AEM and is now also useful as a high resolution elemental mapping technique. Electron energy loss spectroscopy (EELS) vftiile not as well developed for quantitative analysis gives additional chemical information in the fine structure of the elemental absorption edges. EELS avoids the problem of spurious x-rays generated from areas of the spectrum remote from the analysis area. 

Electron energy loss spectroscopy An analytical technique used to characterize the chemistry, bonding, and electronic structure of thin samples of materials. It is normally performed in a transmission electron microscope. The inelastically scattered electron beams are spectroscopically analyzed to give the energy spectrum of electrons after the interaction. 

As noted in the introduction, vibrations in molecules can be excited by interaction with waves and with particles. In electron energy loss spectroscopy (EELS, sometimes HREELS for high resolution EELS) a beam of monochromatic, low energy electrons falls on the surface, where it excites lattice vibrations of the substrate, molecular vibrations of adsorbed species and even electronic transitions. An energy spectrum of the scattered electrons reveals how much energy the electrons have lost to vibrations, according to the formula ... 

Experimental data can be obtained by ultra-violet absorption spectroscopy, electron energy loss spectroscopy and photoelectron spectroscopy. UV absorption and EELs have been described briefly in Chapter 3. The former provides information only about the band-gap, while EELs gives more general information about the conduction bands. Both X-rays and UV photons can be used to generate photoelectrons these two methods are given the acronyms XPS and UPS. The energy spectrum of the emitted electrons provides information about the density of electron states in the valence bands. In principle the size of the band gap can be obtained, but care must be taken as the absolute energy... 

In order to show that the strongly bound species was actually an EpB molecule, high-resolution electron energy loss spectroscopy (HREELS) was used to study the species present at the various dosing temperatures. When dosed at lower temperatures, most of the observed peaks in the HREELS matched those of the vibrational spectrum of liquid EpB, suggesting that intact EpB is interacting with the silver surface at lower temperatures. However, the silver surface dosed with EpB at 300 K showed noticeable differences in the HREELS spectrum. In addition, DPT calculated vibrational frequencies of the surface bound oxaraetallacylce matched well with those determined experimentally. 

Figure 7.26. Electron energy-loss spectroscopy (EELS) spectra. Shown (top) is a representative EELS spectrum of a nickel oxide sample. A typical EELS spectrum shows a zero-loss peak that represents the unscattered or elastically scattered electrons, the near-edge fine structure (ELNES), and extended energy-loss fine structure (EXELFS). Also shown (bottom) are the fingerprint regions of an EELS spectrum, just beyond the core-electron edges, which provide information regarding the detailed bonding and chemical environment of the desired element.

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