NMR study of angular momentum relaxation in fluids. II. Mixtures of CF4 with inert gases

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Abstract
The effects of density and temperature on the angular momentumcorrelation time, τ J , in binary fluid mixtures of CF4 with Ar and Ne, respectively, are reported. The 19F spin–lattice relaxation times,T 1, were measured at 56.4 MHz for 0.1, 0.25, and 0.6 mole fraction CF4 in Ar and Ne from 273 to 373 °K and pressures up to 2040 atm. The spin‐rotation interactions provide the dominant relaxation mechanism for the fluorine nuclei. The experimental τ J data for CF4 infinitely dilute in Ar and Ne in the high density region (ρ≳2ρ c ) are successfully interpreted in terms of the rough hard sphere model (RHSM) modified for use in binary mixtures. The values of the parameter a 12 characterizing the collisional efficiency of angular momentum transfer are obtained for CF4–Ar and CF4–Ne systems. The variation of τ J with mole fraction in these binary mixtures in the dense fluid region was also successfully interpreted in terms of the RHSM indicating that attractive forces are not important in determining the magnitude of the collisional efficiencies a i j . At intermediate and low densities, τ J as a function of mole fraction deviates from the RHSM. As in Paper I, these deviations are interpreted in terms of the effect of attractive forces on the radial distribution function at contact.