To facilitate comparisons between different size Ptn and PtnGem samples, Fig. plots the numbers of C2D4 molecules that adsorbed, desorbed, and decomposed during the TPD sequences for Ptn/alumina and PtnGem/alumina, including the Pt4/alumina sample that was flashed to 750 K prior to the TPD sequence. The results for a Pt4Ge/alumina sample that was heated to 750 K twice prior to the first C2D4 TPD run (Table ) are not plotted because they were essentially identical to those for Pt4Ge from Fig. C/Pt4Ge, 1.4 C/Pt7Ge2, and 1.8 C/Pt11Ge4, i.e., the carbon accumulations per PtnGem cluster varied weakly with increasing cluster size, such that the C atom/Pt atom ratios decreased from ~0.35 for Pt4Ge to just 0.16 for Pt11Ge4, implying that cluster size continued to be a controlling factor over the TPD sequence. Note that the fact that up to ~2 C atoms can accumulate per cluster with little effect on the TPD temperature dependence or intensity implies that carbon deposition has minimal effect on the strength and number of C2D4 binding sites on PtnGem.