,9 F-spin-lattice relaxation rates R i have been investigated in fluid fluoroform in the temperature range 150 K < T < 450 K and at pressures up to p = 200 MPa. Previous measurements of the self-diffusion coefficient D have been supplemented to cover the same p, r-interval. Within the rough hard sphere (RHS) approximation a temperature independent RHS diameter d and a strongly temperature dependent rotation-translation coupling A RT are obtained. Both parameters are also compared with those obtained in a series of related halomethanes. The total 2 D-, 1 H-and 19 F-relaxation rates in CDF 3 and CHF 3 are decomposed into their respective quadrupole, dipolar and spin-rotation contributions and orientational and spin-rotational correlation times are extracted from these rates. It is shown that they are in good agreement with the predictions of the Fokker-Planck-Langevin model. Inertial effects influence the molecular dynamics at high temperatures and low densities. The agreement of self-diffusion coefficients and orientational correlation times with MD-simulation data is very satisfactory.

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The dynamic properties of water molecules coordinated to simple ions (alkali-, alkali earth halides) in undercooled solutions have been investigated with NMR. Relaxation time studies at low temperatures provide details of molecular motions as well as certain features of the local arrangement in the coordination sphere of these ions.Ber. Bunsenges. Phys. Chem. 94, 342-348 (1990)

Abstract. The dynamic properties of water molecules coordinated to simple ions (alkali and alkali-earth halides) and hydrophobic ions (tetraalkylammonium (TAA) halides) in supercooled solutions have been investigated with KMR. The study of spin-lattice relaxation rates and self-diffusion coefficients as functions of temperature, pressure, Larmor frequency and concentration reveals characteristic features of molecular motions close to the lowtemperature limit of the metastable phase (percolation transition and glass transition) and provides certain details of the local arrangement of water molecules in the coordination sphere of these ions. The intramolecular flexibility of the alkyl chains of the hydrated TAA cations has been investigated also. The dynamics of the methyl group reorientation provide a sensitive probe of structural differences in these solutions.

Aqueous emulsions of potassium-and cesium halides in cycloalkane mixtures can be undercooled at a pressure of 225 MPa to temperatures around 170K. In these emulsions deuterium spin-lattice relaxation times T 1 have been determined as function of salt concentration, temperature and pressure at magnetic fields of 2.4 Tesla and 7.0 Tesla. The frequency and temperature dependence of the relaxation time curves is described quantitatively within a motional model which is consistent with known local structural features in these solutions. Model parameters deduced are compared with those obtained in related studies of the other alkali-halides, and conclusions are drawn regarding the influence of structure and composition on molecular motions.