The adsorption of ethylene dioxide (1.4-dioxane) on a silver (110) surface

Abstract

We have studied the interaction of 1.4-dioxane (= ethylene dioxide (CH 2) 4O 2) with a silver (110) surface between 90 and 750 K by means of low-energy electron diffraction (LEED), temperature-programmed thermal desorption spectroscopy (TPD), high-resolution electron-energy loss spectroscopy (HREELS), and work function (ΔΦ) measurements. Dioxane adsorbs molecularly with a high initial sticking probability; up to 600 K there is no indication of dissociation. In TPD, up to 5 different binding states can be distinguished, which are associated with the population of individual dioxane layers. The desorption temperature of 220 K for the highest-lying state (desorption energy ( E∗ ≈ 60 kJ/ mol ) indicates an interaction which (although primarily of physisorptive character) contains non-negligible “chemical” contributions. Combined LEED, vibrational loss and ΔΦ measurements indicate that the dioxane molecules of the first layer adsorb in their characteristic “chair” configuration where the oxygen atoms can specifically interact with Ag surface atoms. This also leads to a preferential ordering of the adsorbed molecules within the first layer. This “orientational” effect of the Ag surface structure is increasingly lost as multilayer formation and condensation of dioxane takes place, although an energetic influence of the Ag surface can be seen in TPD up to the third layer.