TCE Adsorption Properties on Surfaces

Based on previous results [7] obtained on MgO(lOO) and interesting findings herein, the adsorption properties with varying coverages of TCE were studied with EES and TPD on the single crystal surfaces MgO(100),Mo(100), andMo(112). 

The Pt(l 11) surface is used for comparison to previous EES studies, where TCE only weakly adsorbs [8] in contrast to strong interaction for ethene [39-41] and further acts as a reference system for the later measurements on clusters (Sect. 4.4.2). The measurements on the two Mo surfaces are preformed to investigate the influence of the crystal plane on the adsorption properties (e.g. geometry). 

The data recorded ranges from the submonolayer to the multilayer coverage regime and is compared the gasphase PE spectra of TCE [5] (see Appendix Sect. A.3.5). For interpretation of the data the previously mentioned data treatment procedures (Sects. 2.2.3 and A.1.5) are applied with successful extraction of previously superimposed features in the spectra. 

A similar behaviour can be seen for Mo(lOO), where the P peak (physisorption) appears above 0.05 tce/sa and the peak maximum shifts with increasing dosage from 200 to 143 A. Feature a attributed to condensed molecules, starts from 0.15 tce/sa on and the peak maximum shifts from 125 to 129 K. The corresponding integral areas of both peaks p and a for Mg0(100)/Mo(100) andMo(lOO), are shown in Fig.4.12 and show a similar trend. The physisorbed layer is filled at a coverage of 0.15 tce/sa, as the integrated area of the peak p stays stable and only the condensed molecules add to the total integral area. 

The fact, that the peak maxima of the p feature shifts to lower temperatures might be attributed to an order of desorption greater than one [42] on the other hand the observed temperature shifts can be related as well to lateral interactions applying the previously suggested depolarization model for Mg0(100)/Mo(100). At low coverages van-der-Waals interactions between the TCE molecules and the 

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