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The extent of adsorption at 295 and 78 K and the thermal desorption of CO from Pd, Ag, and PdAg alloy films have been measured in an ultrahigh vacuum system. The adsorption data indicated that the surface of the alloys studied in this paper was enriched by Ag. Desorption spectra revealed several adsorption/desorption states, designed as γ 1 , γ 2 , α 1 , α 2 , and β . The nonspecific, most weakly bound γ 1 -state was observed with all adsorbents. The γ 2 -state, also weakly bound, was observed only on Pd. The α 1 - and α 2 -states were observed on Pd and PdAg alloys; they were completely missing on Ag. The population of α-states decreased with increasing Ag content. This is explained by assuming that upon alloying of Pd with Ag the number of large ensembles necessary for strong adsorption decreases.

The temperature programmed desorption of hydrogen from platinum films has been measured in a U.H.V. system by means of a mass spectrometer. The parameters varied were the extent of adsorption, the duration of the adsorption process and the heating rate during desorption. For maximum coverage three desorption peaks have been observed in temperature-programmed desorption: γ (120 K), β1 (200 K) and β2 (330 K). The population of the γ state varies with the duration of pumping at 78 K before adsorption is started, and the population of the β2 state is dependent on the duration of adsorption at room temperature. The isosteric heat of adsorption for high coverages has been measured and varies from 8 to < 2 kcal/Mol for coverages from 7 to 12.1014 mol/cm2 geometric surface.

The extent of CO adsorption has been measured at 295 K and the thermal desorption of CO has been followed on Ni and NiCu films prepared in an ultrahigh vacuum apparatus. The total extent of adsorption revealed a different behavior than the extent of hydrogen adsorption studied previously; an explanation involving gas-induced surface enrichment of alloys is suggested. An irreversible gas-induced enrichment has also been observed upon repeated runs of the thermal desorption of CO. The thermal desorption reveals the existence of two weakly bound states γ1 and γ2 and two more strongly bound states α1 and α2 on Ni and Ni alloys. Cu reveals only the weakly bound states γ1 and γ2. The population of various states varies with the Cu content as well as the chemisorption bond strength of the α2-species. Suggestions are made on the adsorption modes of CO.