Pt signal recovery occurred between 650 and 750 K, even though little additional desorption would have occurred. Because only carbon would have been left on the surface at 650 K, the 55% Pt attenuation implies that the carbon atoms were initially bound in sites on top of the clusters, and the recovery of Pt signal above 650 K implies that these carbon atoms migrated to sites where they caused little attenuation of Pt ISS signal. Such sites could include carbon bound within or beneath the cluster surface layer, or bound to the alumina support.