14. MONITORING AGENCY NAME A AODRESS(it different from Controingi Olfe&) IS. SECURITY CLASS. (of this,.pofl.) Unclassified

To be published in Surface Science IS. KEY WORDS (Continue on,e.'ere @ ald, it necessary end idgnlf by block nam.bes') Ethylene; chemisorption; palladium (111) surface; surface reaction; ethylidyne; vibrational spectroscopy; electron energy loss spectroscopy at high resolution. C*~ZO. ABSTRACT (Continue on reverse side it necessary and idenify by block nuembo,) u-I> The chemisorption and surface reactivity of ethylene on a palladium (111) surface near room temperature has been studied by high-resolution electron energy loss spectroscopy (EELS). The C2H4 molecule reacts with the Pd(lll) surface to form a rather stable surface species which is identified ags ethy-S lidyne (, C-CH3) by analysis of the EELS vibrational spectra. This molecule is also formed on Pt(lll) and Rh(lll) and is believed to be symetrically bonded at threefold surface sites. Angle-dependent EELS spectra are reported and show-the relative importance of imioact And dMnnla Pelt~t Ant mihnm-DD I o~m 1473 EDITION Of ' IO 65 IS OBSOLETE IhLSIJA 3 S/N 01 02.LF-01 4-6601 SEURTYCL ASIFIC TIHD