High Pressure NMR Study of the Molecular Dynamics of Liquid Fluoroform and Deutero‐Fluoroform

Abstract

Abstract The 2 D‐, 1 H‐ and 19 F‐spin‐lattice relaxation rates R 1 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 , T ‐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.