Ethylene oxide adsorption on K-modified Ag(110)

Abstract

Ethylene oxide (Et-O) adsorption on clean and potassium precovered Ag(110) was studied using LEED, angular resolved photoemission spectroscopy (ARUPS), high resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). The binding of Et-O towards clean Ag(110) is weak, complete molecular desorption occurs below 200 K. LEED and spectroscopic data suggest a binding of Et-O to Ag(110) via the oxygen atom in a short bridge adsorption site. Low K precoverages, (θ(K) < 0.3), lead to significant changes in the Et-O/Ag(110) bonding configuration. The TDS peak temperature for low Et-O coverages shifts by ΔT≈ 55 K to higher temperature. However, in the low coverage range of θ(K), Et-O adsorption is still molecular. For higher K precoverages θ(K) ⩾ 0.7, the interaction character between Et-O and K changes drastically. An Et-O + K reaction layer is formed with thermal stabilization to temperatures ⩾ 450 K. This reaction layer is suggested to be due to an Et-O ring breaking reaction at ⩽, 200 K in the presence of metallic K and a polymerization into a larger compound.