High resolution electron energy loss electronic study

Figure 2 Schematic of a 127° high-resolution electron energy-loss spectrometer mounted on an 8-in flange for studies of vibrations at surfaces.

In recent years there is a growing interest in the study of vibrational properties of both clean and adsorbate covered surfaces of metals. For several years two complementary experimental methods have been used to measure the dispersion relations of surface phonons on different crystal faces. These are the scattering of thermal helium beams" and the high-resolution electron-energy-loss-spectroscopy. ... 

The reactions of ethylene, water, and methanol with coadsorbed oxygen on Pdf 100) were studied with temperature programmed reaction spectroscopy (TPRS) and high resolution electron energy loss spectroscopy (EELS). 

Ammonia oxidation was a prototype system, but subsequently a number of other oxidation reactions were investigated by surface spectroscopies and high-resolution electron energy loss spectroscopy XPS and HREELS. In the case of ammonia oxidation at a Cu(110) surface, the reaction was studied under experimental conditions which simulated a catalytic reaction, albeit at low... 

Recent studies using high resolution electron energy loss and photoelectron spectroscopy to investigate the effect of sulfur on the CO/Ni(100) system are consistent with an extended effect by the impurity on the adsorption and bonding of CO. Sulfur levels of a few percent of the surface nickel atom concentration were found sufficient to significantly alter the surface electronic structure as well as the CO bond strength. 

Welipitiya etal. [132] have studied adsorption and desorption of ferrocene on Ag(lOO), applying photoemission and thermal desorption. The initially adsorbed surface species closely resembled that of molecular ferrocene. The molecule was adsorbed with the cyclopentadienyl ring ligands parallel to the surface. Wood-bridge etal. [133] have performed the high-resolution electron energy loss spectroscopy (HREELS) andXPS studies of ferrocene on Ag(lOO). Researchers from the... 

The same system, i.e., C2H2 on Pt(l 11) has also been studied by ultraviolet photoelectron spectroscopy (UPS), by high resolution electron energy loss spectroscopy (HREELS), and by thermal desorption spectroscopy (TDS). The authors have all... 

The success of the isotope dilution experiment for CO on Pt(lll) was accompanied by a serious difficulty in reconciling the magnitude of the shift, which determines Oy/3Q), with the intensity of the band, which also determines Oy/3Q). When due allowance is made for the resultant surface field and geometric factors (36) in RAIR spectroscopy the intensity is almost consistent with the vibrational polarizability av = 0.057 X3 (39), corresponding to the gas phase intensity, as has been concluded for CO adsorbed on copper films (40) from infrared studies and for CO on Pt(lll) (41) and Cu(100) (42) from high resolution electron energy loss spectroscopy. This value of av is an order of magnitude smaller than that deduced from the frequency shift. 

Figure 1. Schematic oj the high resolution electron energy loss spectrometer used in these studies. The dispersive elements are 127° cylindrical sectors.

The preference of Eq. (21a) for C02 dissociation may be well anticipated. It has been shown [see, for example, the high-resolution electron energy loss spectroscopy (HREELS) studies of C02 on Re(001) (71a), ultraviolet/ X-ray photoelectron spectroscopy (UPS/XPS) studies of C02 on Fe(lll) and Fe(l 10) (37), and computer simulations for C02 on Pt(l 11) (71b)] that the molecule is practically undistorted (symmetric and linear) in the ground chemisorbed state but strongly distorted (nonsymmetric and bent) as an intermediate preceding the dissociation C02 s — COs + Os. So, there is a good reason to believe that in the transition state the coordinated C—O bond is strongly expanded [by 0.12 A (71b)] and becomes very weak. But the weaker the C—O bond (xc0 — 0), the more accurate is Eq. (21a). 

In contrast to the acetaldehyde decarbonylation, reactions with ethanol over Rh (111) did not lead to formation of methane but rather to an oxametallocycle via methyl hydrogen abstraction. These data suggest that ethanol formed over supported rhodium catalysts may not be due to hydrogenation of acetaldehyde. This study shows how surface science studies of model catalysts and surfaces can be used to extract information about reaction mechanisms since the nature of surface intermediates can often be identified by methods such as temperature programmed desorption and high resolution electron energy loss spectroscopy. 

Chen PJ, Colaianni ML, Wallace RM, Yates JT Jr (1991) Dissociative adsorption of PH3 on Si( 111) — (7x7) a high resolution electron energy loss spectroscopy study Surf. Sci. 244 177-184... 

Most studies on deposition of fullerenes on semiconductor surfaces have focused on silicon9 28 and, to a much less extent, on GaAs. Earlier experimental work using HREELS (high-resolution electron energy loss spectroscopy) on C60 adsorption on Si (100)2 x 1 surface suggested that the molecular attachment to the... 

There is a number of vibrational spectroscopic techniques not directly applicable to the study of real catalysts but which are used with model surfaces, such as single crystals. These include reflection-absorption infrared spectroscopy (RAIRS or IRAS) high-resolution electron energy loss spectroscopy (HREELS, EELS) infrared ellipsometric spectroscopy. 

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