Density dependence of the molecular dynamics of fluid CH₃ F and CF₃ H studied by NMR

Abstract

The dynamic behaviour of compressed CH3F and CF3H has been studied between 150 and 400 K and to pressures of 200 MPa by measuring the spin-lattice relaxation times (T1) of the proton and fluor nuclei. Also the deuteron T1 of CD3F and CF3D were obtained in the whole p, T range. Both substances reveal a significant non-Arrhenian behaviour when the whole temperature range is studied.
In addition the self-diffusion coefficients of these compounds and of their analogues CH3Cl, CH2Cl2 and CHCl3 have been investigated. The data obtained can be described best by the rough hard sphere model. It is found, that the rough hard sphere diameter (dRHS) of all compounds is almost independent of temperature (CF3H dRHS=0.39nm, CH3F dRHS=0.35nm, CH3Cl: 0.40nm, CH2Cl2: 0.44nm, CHCl3; 0.48 nm).