in obtaining the electron paramagnetic resonance data. We also wish to thank Dr. Richard Hendler for the use of his visible spectrometer and for numerous helpful discussions. J.S.V. acknowledges receipt of an NIH Senior National Research Service Award. Registry No. Cytochrome c, 9007-43-6. (26) Kimelberg, H. K.; Lee, C. P. J. Membr. Biol. 1970, 2, 252-262. (27) TRIS, tris(hydroxymethy1)aminomethane. HEPES, N-(2-hydroxy-(25) Snyder, R. G.; Straws, H. L.; Ellinger, C. A. J. Phys. Chem. 1982, 86, 5145-5150. ethyl)piperazine-N'-2-ethanesulfonic acid.Abstract: The interaction of ethylene with the Ru(001) surface has been investigated via high-resolution electron energy loss spectroscopy and thermal desorption mass spectrometry. Following desorption of an ethylene multilayer at 110 K, di-o-bonded molecular ethylene is present on the surface. Competing desorption of molecular ethylene and dehydrogenation to form adsorbed ethylidyne (CCHJ and acetylide (CCH) as well as hydrogen adatoms occur between approximately 150 and 260 K. The ethylidyne is stable to approximately 330 K, whereupon it begins to decompose to carbon and hydrogen adatoms. The desorption of hydrogen occurs in a sharp peak centered at 355 K, resulting from simultaneous ethylidyne decomposition and desorption of surface hydrogen. Further annealing of the overlayer to 380 K causes cleavage of the carbon-carbon bond of the acetylide, creating carbon adatoms and adsorbed methylidyne (CH). The methylidyne decomposes above 500 K with accompanying hydrogen desorption, leaving only carbon adatoms on the surface at 700 K.

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