Thus, the probability of carbon deposition during this 1 st TPD run was ~one-fourth that for the Pt4/alumina samples. By the 6 th TPD cycle, the number adsorbing C2D4 molecules was still ~1.46/cluster, of which 91% desorbed intact, with the balance decomposing to liberate D2 and deposit just ~0.28 C/Pt4Ge cluster. Thus, during the 2 nd TPD for Pt4Ge/alumina, the number of ethylene adsorbing per cluster was ~41% lower than in the 1 st TPD for Pt4/alumina, but by the 6 th TPD, the number was ~20% higher for Pt4Ge. We interpret this to imply that addition of a Ge atom reduced the initial number of ethylene binding sites, but the binding sites, and particularly the catalytically important strong/high temperature binding sites, survived much better under reaction conditions for Pt4Ge than for Pt4.