Direct observation of tetrahedral hydrogen jumps in ice Ih

Using deuteron NMR, spin alignment tetrahedral jumps of 2H in deuterated polycrystalline hexagonal ice (Ih) have been observed. Both geometry and time scale of the process are determined directly. At T=230 K the correlation time of these jumps is 0.21(3) ms. The tetrahedral hydrogen jumps turn out to scatter—most characteristically for the disorder within the hydrogen subsystem—randomly about the tetrahedral angles by about ±3° with a correlation time of 0.5(1) ms. With additional experiments on specifically doped ices it is shown that these tetrahedral jumps are due to diffusing Bjerrum vacancies.