Vibrational spectroscopy VEEL

Our article has concentrated on the relationships between vibrational spectra and the structures of hydrocarbon species adsorbed on metals. Some aspects of reactivities have also been covered, such as the thermal evolution of species on single-crystal surfaces under the UHV conditions necessary for VEELS, the most widely used technique. Wider aspects of reactivity include the important subject of catalytic activity. In catalytic studies, vibrational spectroscopy can also play an important role, but in smaller proportion than in the study of chemisorption. For this reason, it would not be appropriate for us to cover a large fraction of such work in this article. Furthermore, an excellent outline of this broader subject has recently been presented by Zaera (362). Instead, we present a summary account of the kinetic aspects of perhaps the most studied system, namely, the interreactions of ethene and related C2 species, and their hydrogenations, on platinum surfaces. We consider such reactions occurring on both single-crystal faces and metal oxide-supported finely divided catalysts. 

C. Vibrational Electron-Energy-Loss Spectroscopy (VEELS) (21)... 

VEEL or RAIR spectroscopy to provide insight into temperature-dependent surface reactions. The TPD technique also provides information about the overall C/H composition of the hydrocarbon layers at different temperatures. Whereas we have made reference to, and taken into account, experimental results obtained from the use of such nonvibrational techniques in many cases, particularly when considering spectral interpretaions, it has not been feasible for us to systematically cover such papers that do not also include vibrational spectroscopic work. 

The present-day literature contains many more spectra obtained from singlecrystal metal surfaces by VEELS than by RAIRS. However, the much higher resolution available from the more recently developed RAIRS technique and its capability of operating in the presence of a gas phase suggest that it will contribute increasingly important information in the hydrocarbon adsorption field. The three spectroscopic techniques discussed above are much the most important ones in this area, with transmission infrared spectroscopy as the predominantly useful one for work with finely divided samples. A few other vibrational spectroscopic techniques (25) have provided information on adsorbed hydrocarbons, but are at present of more limited or specialized applications. Their principal characteristics are more briefly summarized below. 

VEELS vibrational electron energy-loss spectroscopy... 

VEELS vibrational energy loss electron spectroscopy... 

VEELS SFG vibrational electron energy-loss spectroscopy Sum-frequency generation Yes l° 212-218 No... 

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