Figure 3.
Temperature dependence of the absorption enthalpy ΔHabs for hydrogen and deuterium: H2 → 2Hbulk (filled circles)32 and D2 → 2Dbulk (open squares).37 The solid line shows the fit obtained using the desorption/diffusion model described in the Methods section. The fit relies on three parameters describing the 1D diffusional potential of Hbulk/Dbulk, from which the partition function of Hbulk/Dbulk was computed. The dashed line marks the temperature and isotope independent value obtained by Engel and Kuipers.3