High pressure nuclear magnetic resonance measurement of spin–lattice relaxation and self-diffusion in carbon dioxide

Spin–lattice relaxation time and self-diffusion coefficient in 13CO2 have been measured on the four isotherms 0, 25, 50, and 75 °C at pressures ranging from 10 to 500 bar. The governing relaxation mechanism in this range is shown to be spin–rotation relaxation. Low pressure T1 data are adequately described by Gordon’s theory, while high pressure T1 data agree semiquantitatively with the diffusion model proposed by Hubbard. The low density self-diffusion coefficient behavior is in agreement with the kinetic theory of the dilute gas phase. Strong divergence from Enskog theory is observed in the dense gas and liquid phases. The hard-sphere theory predicts the self-diffusion coefficient within ±2% at densities above 1.5 ρc. The simple hydrodynamic theory predicts the self-diffusion coefficient within ±5% at densities above 1.5 ρc.