Experimental evidence for the rough hard sphere model of liquids by high pressure NMR

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Abstract
The NMR 19F spin–lattice relaxation times, self-diffusion constants, and densities have been measured in liquid CCl3F as a function of temperature and pressure. Since spin–rotation interactions provide the dominant relaxation mechanism for fluorine nucleus, the analysis of the T1 data yields the angular momentum correlation time τJ. The density dependence for the spin–rotation relaxation data enables us to calculate the effective hard sphere diameter for liquid CFCl3. In turn these diameters are used in calculation of the self-diffusion constants applying the rough hard sphere model for molecular liquids as recently proposed by Chandler. Our experimental results provide evidence for (i) relationship between τJ and the Enskog relaxation time τE; (ii) validity of the rough hard sphere model for fluids; and (iii) the dependence of diffusion constants upon density in agreement with molecular dynamics calculations by Alder et al.