ISS can also be used to probe changes in cluster/adsorbate morphology during TPD, using the temperature-dependent ISS (TD-ISS) approach shown in Fig. . In essence, TD-ISS involves measuring ISS intensities after dosing a sample with reactants, and then at regular intervals as the sample is heated to drive desorption, sintering, and other processes that also occur during TPD. 60 Unsurprisingly, the Pt intensity remained constant as the sample was heated to 250 K, desorbing C2D4 from sites on the alumina support. The absence of intensity recovery between 250 and 400 K is more interesting, because most of the intact C2D4 desorption from Pt sites would have occurred in that temperature range. This finding is consistent with the proposal that as C2D4 desorption creates empty Pt sites, the remaining C2D4 decomposes, and clearly the D and CxDy fragments occupy these Pt sites so that He + scattering from Pt remains strongly attenuated.