Density dependence of the molecular dynamics of fluid CH3F and CF3H 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 T 1 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 CH3CI , CH2CI 2 and CHCI 3 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 dRH s = 0.39 nm, CH3F dRH s = 0.35 rim, CH3CI: 0.40nm, CH2C12:0.44 nm, CHCI3; 0.48 nm).