ETHYLENE-OXIDE ADSORPTION ON K-MODIFIED AG(110)

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, (theta-(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 DELTA-T almost-equal-to 55 K to higher temperature. However, in the low coverage range of theta-(K), Et-O adsorption is still molecular. For higher K precoverages theta-(K) greater-than-or-equal-to 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 greater-than-or-equal-to 450 K. This reaction layer is suggested to be due to an Et-O ring breaking reaction at less-than-or-equal-to 200 K in the presence of metallic K and a polymerization into a larger compound.