An experimental study of the proton spin-lattice relaxation time T1 has been made for H2O over the temperature interval from −16 to 145°C. It is found that after correction for spin-rotational interaction, the experimental T1 behavior can be represented by the double exponential form of the rate expression used to treat the relaxation for the quadrupolar nuclei 2H and 17O in water. The oxygen-17 data are used to calculate the intramolecular contribution to the proton T1. The activation energies E1=9.4± 0.8 kcal/mole and E2=3.6± 0.1 kcal/mole for the two contributions to the intermolecular relaxation are in sufficiently good agreement with those for the intramolecular relaxation to indicate that the relaxation mechanism is the same in both cases. This mechanism involves two processes. The data indicate the process dominant at high temperature can be described as a rotational diffusion where the amplitude of angular motion increases with increasing temperature.

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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.

Radiofrequency pulse techniques have been used to measure the deuteron spin lattice-relaxation time for DgO in certain organic solvents. In particular, we have examined solutions where infrared observations indicate that the properties of the dissolved water molecules are only slightly altered from the gas state and where there is little evidence for strong intermolecular complex formation. Concentration dependence studies were used to derive the relaxation times for infinite dilution of DzO in the organic solvent. The TI values were combined with deuteron quadrupole coupling constants calculated from infrared data to give values for the molecular reorientational correlation times, f Q, As expected, these correlation times are much shorter than reorientational correlation times calculated from the Debye-Bloembergen-Purcell-Pound equations. We have briefly considered the implications of these observations with respect to models of water structure where the existence of freely rotating monomers is assumed. species, a hydrogen-bonded species and a nonhydrogenbonded species, Further, as Frank has pointed OUt,z the persistence of the tetrahedral structure in the liquid (1) Based on work performed under the auspices of the U. 8. Atomic Energy Commission and presented in part before the Physical