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The contribution of intramolecular vibrations to the observed structure of liquid water J. Chem. Phys. 82, 5289 (1985); 10.1063/1.448606 Ultrasonic measurements and liquid structure of DMSO-water mixture Proton spin-lattice relaxation times (T 1) of water and dimethyl sulfoxide (DMSO) in H20-DMSO (I), H 2 0-DMSO-d 6 (II), and D 2 0-DMSO (IV) systems at 9.8, 18.7,29.9, and 41.4°C exhibited minima near 0.65 mole fraction of water (X H,O)' The depth of the minimum, relative to T 1 values at higher and lower X H,O' increased as the temperature was lowered. The intramolecular contribution to the relaxation of DMSO protons was always greater than the intermolecular DMSO-DMSO contribution and the former showed a minimum at X D 0::::0.6 as compared with the latter's minimum at X D,0::::0.4-0.6. There is almost no contrib~tion to water proton T 1 from the interaction of water protons-DMSO protons in the DMSO·rich mixtures, while this contribution is rather significant in the DMSO·poor mixtures. The proton chemical shifts of water with reference to DMSO protons (over a temperature range of -60-45'C) moves to higher fields with rising temperatures, and this temperature dependence is affected considerably by the changes in composition. All these experimental results suggest the presence of strong intermolecular interactions between water and DMSO molecules that contribute to the "structuring" of this binary mixture. The structure of this liquid system is very sensitive to composition and temperature.In this work the dynamic liquid structure of DMSOwater mixtures was investigated by measuring T 1 , T 2 , and chemical shift values of the protons of both compo-

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