Temperature dependence of water self-diffusivity in pure polycrystalline ice and in ice doped with HCl: Fast thermal desorption spectroscopy study

We report the results of a fast thermal desorption spectroscopy study of the H/D isotopic exchange kinetics in a few micrometer thick, pure polycrystalline ice film and in ice films doped with HCl. Using the isotopic exchange reaction as a probe of molecular transport in ice, we were able to determine the effective water-self diffusion coefficients, Deff, in pure and doped polycrystalline ice at temperatures ranging from -18 to -1 °C. In the case of pure polycrystalline, Deff demonstrates an Arrhenius dependence on temperature with an effective activation energy of 69 ± 3 kJ·mol -1 and a pre-exponential of 10 9±0.5 μm 2 ·ms -1 up to -2 °C. According to our analysis, the self-diffusion coefficient of water at the grain boundaries also shows an Arrhenius dependence on temperature with an activation energy of 69 ± 3 kJ·mol -1 and pre-exponential of 10 11±1 μm 2 ·ms -1 . However, upon the addition of 0.04% of HCl into the polycrystalline ice results in a marked deviation of Deff from Arrhenius law at -8 o C, which we attribute to DRAFT