Relaxation Processes in Water. The Spin–Lattice Relaxation of the Deuteron in D2O and Oxygen-17 in H217O

Abstract

Proton spin-lattice relaxation rate in supercooled H2O and H2 17O under high pressure An experimental study of the deuteron relaxation time TI has been made over a temperature range -18-178°C. The equation for the temperature dependence of the relaxation time is of the formThe data are interpreted in terms of an equilibrium leading to a species which relaxes by an isotropic rotational diffusion process. Using transition rate theory and a quadrupole coupling constant derived for the relaxing species from dielectric data, heats and entropies are calculated for both the equilibrium and rate processes. For the equilibrium ~H=6.8±0.2 kcal mole-I and ~S=24.8±0.9 e.u. mole-I. For the rate, ~H*=2.50±0.06 kcal mole-1 and ~S*=3.6±0.1 e.u. mole-I. Similar measurements for the oxygen-17 relaxation time Tl over the temperature interval -14-180°C yield for the equilibrium ~H=5.6±0.3 kcal mole-1 and ~S=20.7±1.4 e.u. mole-I. For the rate, ~H*=2.43±0.08 kcal mole-1 and ~S*=3.9± 0.2 e.u. mole-I. The results are discussed in terms of models for the water structure, the species present in the liquid, the relaxation process and molecular motion in the liquid.

Calculation of Quadrupole Coupling Constants: From Gas to Liquid

“…The average of 261 kH z Unauthenticated Download Date | 5/11/18 5:29 PM from Table 4 is probably about 3% too large, as we know th at the gas phase coupling calculated on the same level of approxim ation is 3% larger than the experimental value. The corrected value for the liquid is then 254 kH z in excellent agreement with the newest experimental values of Leyte and coworkers [24,25] H indm an and coworkers [26] of 258.6 kHz. We cannot give an accurate error for our coupling constant but would estimate it to be of the same size as the above experimental errors, i.e.…”

Solid state water motions revealed by deuterium relaxation in 2H2O-synthesized kanemite and 2H2O-hydrated Na+-Zeolite A

“…The ability to invert the part of the sharp central resonance arising from the population of water molecules experiencing C 2 and octahedral jumps of their O-2 H bonds persists to slightly lower temperatures, presumably since k C 2 >> qcc and k exch > qcc. Experimentally, the loss of the ability to invert the sharp central [35]. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this paper.…”

“…15. The experimental deuterium T 1 data for the sharp central resonance of 2 H 2 O-synthesized kanemite at 46.03 (purple squares) and 76.77 MHz (dark blue diamonds); T 1 data obtained at low temperature for the fast-relaxing component at 46.46 MHz (purple crosses), and T 2 data obtained with the double echo CPMG experiment at 76.77 MHz (orange squares) The temperature dependent T 1 = T 2 values (black triangles) for bulk 2 H 2 O at atmospheric pressure are shown for comparison[35]. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this paper.…”

Rotational dynamics in supercooled water from nuclear spin relaxation and molecular simulations

“…Hindman et al described the temperature dependence of their τ R data for H 2 O and D 2 O by a sum of two Arrhenius terms with temperature-independent coefficients and interpreted these components in terms of a two-state (interstitial-framework) mixture model for liquid water structure. 26 Since this functional form is not unique, it seems precarious to attach physical significance to the fitted parameters. Our τ R data can also be described reasonably well by a double Arrhenius function, but Eq.…”

“…25 These quadrupolar nuclides have been used extensively to study rotational dynamics in water, also in the supercooled regime. [26][27][28][29][30][31] In fact, no other experimental technique can provide information about water dynamics down to the practical limit of supercooling. On the other hand, because molecular rotation even in supercooled water (at ambient pressure) is fast compared to the highest accessible NMR frequencies, the nuclear spin relaxation rate only yields the time integral of the TCF, that is, the integral rotational correlation time.…”