The diffusion of molecular hydrogen adsorbed in zeolite 13X at high coverages was studied using quasi-elastic neutron scattering at 0 to 60K. No diffusive motion was observed, within instrumental resolution, below 20K, well above the bulk melting point of H2, in contrast to NMR studies. The diffusive motion of the adsorbed H2 could be described by a liquid-like jump diffusion model above 35K. The diffusion coefficient exhibited Arrhenius behavior, with Do = 1.2 x 10-8m2/s. The inelastic scattering spectrum was also studied. The scattering consisted of several peaks superposed on a broad background extending from 1meV to above 100meV and was consistent with rotational transitions for a hindered rotor in a strong orientational potential with a broad distribution of barrier heights.

A Quasi-Elastic and Inelastic Neutron Scattering Study of H2 in Zeolite. H.Fu, F.Trouw, P.E.Sokol: Journal of Low Temperature Physics, 1999, 116[3-4], 149-65