Translational Diffusion Of Water Molecules Research Articles

Reorientation and diffusion of water molecules in xenon hydrate and other structure.

In contrast to ice Ih, in which the translational diffusion of water molecules is faster than their reorientation, the good correlation between proton magnetic resonance line narrowing and dielectric relaxation rates of the water molecules which form the structure I clathrate hydrate lattice suggests that reorientation is the faster process. This is certainly so for the hydrate of ethylene oxide-d4, for which two separate line-narrowing regions are observed. Both processes depend on the nature of the guest molecule.

Nuclear Magnetic Resonance of the Aquated Proton. II. Chloroauric Acid Tetrahydrate. Phase Transitions and Molecular Motion

Proton and deuterium nuclear magnetic resonance and chlorine-35 nuclear quadrupole resonance of chloroauric acid tetrahydrate, H5O2+AuCl4−· 2H2O has been studied from 180 to 300°K. Phase transitions are observed at 290°K (Solid I↔ Solid II) and at 218°K (Solid II↔ Solid III) in ordinary chloroauric acid tetrahydrate. In the deuterated compound the lower-phase transition shifts upward by 33° to 252°K; an upper-phase transition was not detected below 300°K. The chlorine-35 NQR consists of two lines (1:1 intensity ratio) above the Solid II—III phase transition and three lines (1:2:1 intensity ratio) below this transition. The proton spin—lattice relaxation time T1 of H5O2+AuCl4−· 2H2O exhibits a minimum at 273°K which is assigned to the interbond jump motion of the bridging proton in the H5O2+ ion. The activation energy for this process is 5.7 kcal mole−1 in Solid II and 11.7 kcal mole−1 in Solid III. Rotating frame relaxation times have minima at 200 and 233°K which are assigned to the interbond jump process and a proton exchange process, respectively. The proton exchange process involves rotation of the hydronium ion about the threefold axis and translational diffusion of water molecules between sites which differ in water molecule orientation by 90°. The deuteron resonance of a single crystal and polycrystalline D5O2+AuCl4−· 2D2O is interpreted in terms of the deuterium exchange process. This process has an activation energy of 10.4 kcal mole−1 in Solid II.