Acetylene, spectrum chemisorbed

Figure 5. High resolution ELS spectra of chemisorbed acetylene on Rh(lll) (a) (2 X 2)-CsHt (b) (2 X 2)-C2D and (c) c(4 X 2 -CtHs + H. The vibrational assignments for Spectra (a) and (b) are listed in Table III. Spectrum (c) is discussed in more detail in the next section.

Fig. 4. (A) Spectrum of acetylene chemisorbed on nickel (B) after treatment with Hs. ...

Paraffins, of course, cannot have an associative mechanism and do not adsorb on hydrogen-covered nickel. When adsorbed on bare nickel they behave in a manner similar to ethylene. Acetylene, on the other hand, exhibits a unique behavior. Regardless of the pretreatment of the nickel, acetylene produces the spectrum assigned to chemisorbed ethyl radicals. This indicates extensive self-hydrogenation and the formation of a surface carbide. The idea of a surface carbide is supported by a very large increase in spectral intensity when hydrogen is added to chemisorbed acetylene. 

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