Neutron time-of-flight experiments were performed on hydrogen adsorbed in Na-mordenite at between 35 and 130K and densities of between n = 43 and n = 13 H2 molecules in the unit cell of the zeolite lattice. The quasi-elastically scattered neutrons gave rise to a peak that was not broadened at half-height with respect to the experimental energy resolution of 90μeV (46ns). A Lorentzian broadening at the bottom of the quasi-elastic peak was interpreted in terms of a diffusion model yielding a rotational diffusion constant of 2 x 1011rad/s and a translational diffusion constant of 2 x 10−3cm2/s at 130K and n = 35H2mol/unit-cell.

Diffusive Motion of Hydrogen in Mordenite Studied by Quasi-Elastic Neutron Scattering. R.Stockmeyer: Zeolites, 1992, 12[3], 251–5