The pressure and temperature dependence o f the self-diffusion coefficients D of n-butane, n-pentane, n-hexane, n-decane, trans-2-butene, cis-2-butene and 2-butyne were determined in the liquid state by NM R-techniques at pressure up to 200 MPa and temperatures up to 450 K.The results are taken as tests for the various dynamical models and compared to results obtained by M D calculations. The activation parameters for translational transport and the parameters for the RHS-m odel are derived and discussed.

The self diffusion coefficients D have been measured for a series of linear and branched alkanes between the melting pressure curve and 450 K at pressures up to 200 MPa. The experiments were performed in a strengthened glass cell by application of the pulsed field gradient technique. — The p, T dependence of the data is described by the rough hard sphere model (Chandler) and by the interacting sphere model (Speedy). — The measurements have been extended to binary mixtures of a long chain alkane (tetradecane) and 4 to 12% w/w methane. The addition of relatively small amounts of the lower alkane enhances significantly the translational mobility and reduces the p. T dependence of the self diffusion coefficients of tetradecane.

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