Heat capacity of H2 adsorbed on carbon nanotube bundles

We report on, ongoing measurements of the heat capacity of H-2 adsorbed on, closed-end single-wall carbon nanotube bundles(SWNTB), for 1.5K less than or equal to T less than or equal to 10K and for coverages between 0.0 and 1.4 layers. Coverages are defined from a sharp minimum in, heat capacity isotherms. We determine three distinct regions corresponding to: a) Formation, of lines of atoms in, grooves and large interstitial sites, b) Formation, of a layer over the graphite-like outside surface of the bundle, and c) Beginning of growth of the second layer. Results are correlated to H-2 vapor pressure isotherms and are compared to helium heat capacity measurements done on, the same cell. In, neither He-4 nor H-2 do we observe a 1-d ideal gas regime.