The self-diffusion coefficients D for neat CO2 have been determined in
a wide rho, T range by the Stejskal-Tanner NMR method applying pulsed
field gradients. In our apparatus CO2 supercools readily and the data
could be collected between 223 K and 450 K at pressures up to 200 MPa
. The rho, T dependence of D(CO2) shows significant deviation from har
d-sphere fluid behavior. The rough hard sphere (RHS) model, as well as
the simple hydrodynamic theory show a very unusual temperature depend
ence, when compared to other simple fluids. (C) 1998 American Institut
e of Physics.