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

In situ proton NMR spectra and T₁^0.2em0ex-1 and T₂^0.2em0ex-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 3.60.3em0exGPa gave surprisingly narrow resonances of the H₂ guests. Pressure effects on T₁^0.2em0ex-1 and T₂^0.2em0ex-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.