Anisotropic diffusion in benzene:C13NMR study

We report a ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR measurement of the three distinct diffusion jump rates present in solid benzene (orthorhombic). Diffusion jumps from one a-b plane to another are found to be preferred over jumps within any one plane. The rates of the two kinds of out-of-plane jumps are unexpectedly found to be nearly equal. These findings should serve as a rigorous test of any calculations of diffusion in solid benzene. We have also measured the temperature dependence of the average of the three rates. Our results for the prefactor ${\omega }_0$ agree with previous NMR determinations, but disagree with radiotracer data.