Spectroscopic Study of the Absorption of C2H4 and C2H2 on a Rare-Earth Single Crystal. 1. Metallic Gd(0001)

摘要

The adsorption of ethylene and acetylene on a rare-earth-metal surface, Gd(0001), has been studied primarily by ultraviolet photoemission and Auger electron spectroscopes. Both species adsorb dissociatively on the clean Gd(0001) surface at 165 K to form adsorbed atomic carbon and hydrogen. At slightly higher coverages, carbon-hydrogen bond scission is no longer complete, resulting in a mixture of atomic carbon, CH, and CH2. Sticking probabilities for both species are estimated to be in the range 0.2-0.4. Molecular adsorption occurs at 165 K after passivation of the Gd(0001) surface with adsorbed C and Hx species. As the substrate temperature is increased above 300 K, these molecularly adsorbed species dissociate rather than desorb. Gadolinium carbide is formed at higher temperatures.