NMR study of liquid and supercritical benzene

Density, spin-lattice relaxation time and self-diffusion coefficient of benzene have been measured under vapor-liquid coexistence from room temperature up to above the critical temperature. Measurements were made for four samples with the density in the supercritical region being respectively 0.302, 0.250, 0.154 and 0.101 g cm(-3). The density has been determined by the NMR one-dimensional projection technique, and the Carr-Purcell-Meiboom-Gill method has been adopted to the measurement of the self-diffusion coefficient. The results obtained have been discussed in terms of hard sphere models and various contributions to the relaxation rates have been separated and the correlation times for each molecular motion have been estimated at 470 K. It has been shown that the spin-rotational relaxation is dominant near and above the critical temperature.