Note that the final 750 K Pt intensity was nearly identical to the value measured after a normal TPD run on a separate sample, indicating that the He + exposure during TD-ISS had minimal effect on the final state of the Pt clusters. This final Pt intensity was 82% of the as-deposited value, i.e., some combination of carbon deposition and sintering during TPD caused a small decrease in the fraction of Pt in the surface layer, but clearly the clusters did not sinter into large 3D particles, which would have had resulted in much larger attenuations. The TD-ISS results for Pt4Ge/alumina were quite different (Fig. ). After the 150 K C2D4 dose, the Pt ISS signal was ~28% of the as-prepared value, and the Ge intensity was ~60% of the as-prepared Ge value (~0.04), consistent with the DFT finding that C2D4 binds preferentially to Pt. between 250 and 400 K, spanning the higher temperature C2D4 desorption feature and the lower temperature D2 desorption feature. Additional recovery of both Pt and Ge signals occurred as the temperature was stepped from 400 to 650 K, completing the D2 desorption, but unlike Pt4, there was little additional change above 650 K. These differences reflect the fact that a much larger fraction of C2D4 adsorbed on Pt4Ge would have desorbed intact, with fewer decomposition products present at intermediate temperatures, and less carbon deposited.