Fast molecular transport in hydrogen hydrates by high-pressure diamond anvil cell NMR

In situ proton NMR spectra and T1 -1 and T2 -1 relaxation rates of filled-ice hydrogen hydrates at pressure reveal fast translational motion of the H2 molecules within the ice frameworks. The NMR spectra to 3.6 GPa gave surprisingly narrow resonances of the H2 guests. Pressure effects on T1 -1 and T2 -1 of the H2 indicate that molecular rotation and diffusion contribute together to the relaxation, from which correlation times τrot and τdif were separately determined. Liquidlike fast diffusion of the H2 with little pressure sensitivity was deduced from τdif, indicating that the ice framework allows active guest translation even in extensively compressed states.